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Orbit Electron Configuration of Beryllium (Be) atom is two electrons in first orbit (K) and 2 electron in second orbit (L)

Orbital Electron Configuration of Beryllium (Be) atom is 1s^{2} 2s^{2} which means Beryllium atom have two electrons inside 1s orbital and two electron in 2s orbital

Also we can replace 1s^{2} with [He], therefore electron configuration of Beryllium (Be) is [He] 2s^{2}

**Be** is the symbol for the element Beryllium, which is located at position four of the periodic table. Beryllium has a total of four electrons in its atomic structure. Beryllium is an **Alkaline Metal** which means it form alkaline solution on reaction with water. Alkaline solution means that pH of solution is greater than seven and its basic in nature.

**Electron configuration** refers to the arrangement of electrons in different orbits and orbitals of an atom in a certain order. Depending upon whether electrons are being arranged in Orbits or Orbitals there are two types of electron configurations – **Orbit Electron Configuration** and **Orbital Electron Configuration**.

In this article, I’ve discussed both Orbit and Orbital Electron Configurations of Beryllium (Be) atom.

Table of Contents

## Orbit Electron Configuration of Beryllium (Be)

Niels Bohr, a Danish scientist, was the first to propose the concept of an orbit around an atom. In 1913, he presented a model of the atom to the scientific community. As per this model, the electrons in an atom follow a set path as they go around the nucleus in circular motion.

These set paths are called “Orbits” and are numbered as 1, 2, 3, ……… depending upon their closeness to nucleus of atom. So first circular path around nucleus is numbered as 1, second as 2 and so no. Moreover orbits are also denoted by English letters.

- First orbit – K and have n = 1
- Second orbit – L and have n = 2
- Third orbit – M and have n = 3
- Fourth orbit – N and have n = 4
- and so on.

How many electrons any of these orbits can hold is determined by using formula 2n^{2} where n is number of orbit. Based upon this formula, different orbits in the atom can hold electrons as following.

- First orbit – K (n = 1) can hold 2n
^{2}= 2 (1)^{2}= 2 electrons - Second orbit – L and have n = 2 can hold 2n
^{2}= 2 (2)^{2}= 2 (4) = 8 electrons - Third orbit – M and have n = 3 can hold 2n
^{2}= 2 (3)^{2}= 2 (9) = 18 electrons - Fourth orbit – N and have n = 4 can hold 2n
^{2}= 2 (4)^{2}= 2 (16) = 32 electrons - and so on.

**As Beryllium atom have four electrons, therefore it’s Orbit Electron Configuration will be two electrons in K orbit and two electrons in L orbit.**

### How many electron shells does Beryllium have?

Beryllium have electron configuration 2, 2 which means it have 2 electrons in K shell and 2 electrons in L shell. Therefore Beryllium have **2 electron shells**.

## Orbital Electron Configuration of Beryllium (Be)

Niels Bohr proposed the idea that electrons revolve around nucleus in specific circular paths called Orbits, but later on Heisenberg found out that it’s impossible to determine position and velocity of an electron inside the atom at same time, so how it’s possible that electrons do circular motion on specific paths in an atom.

In later years, Erwin Schrodinger developed a mathematical formula to compute the probability of finding the location of an electron inside an atom.

On the basis of this probability, the location of an electron inside an atom could be represented as the chances of that electron being located in a certain three-dimensional area surrounding the nucleus.

As 3D region can be explained only using 3 parameters, therefore in order to describe where an electron is? inside the atom.

We need three numbers – **Principle Quantum Number (n)**, **Angular Momentum Number (l)** and **Magnetic Momentum Number (m)**.

Therefore Orbits(this concept was proposed by Neils Bohr) are further divided into sub-energy levels called **subshells**. How many subshells an orbit have is equal to Principle Quantum Number (n) of orbit.

Therefore

- First Orbit (K and n = 1) have 1 subshell
- Second Orbit (L and n = 2) have 2 subshell
- Third Orbit (M and n = 3) have 3 subshell
- Fourth Orbit (N and n = 4) have 4 subshell

These sub-energy levels/subshells have specific regions where probability of finding electrons is maximum. These subshells are names as s, p, d, f and have angular momentum numbers as 0, 1, 2 and 3 respectively.

Which type of subshell an orbit have can be determined using Angular Momentum Number (I).

So

If Principle Quantum Number of an orbit is n

Then subshells in that orbit are **0** to **(n – 1)**

If

Angular Momentum Number(l) = 0 that means it’s **s** orbital

Angular Momentum Number(l) = 1 that means it’s **p** orbital

Angular Momentum Number(l) = 2 that means it’s **d** orbital

Angular Momentum Number(l) = 3 that means it’s **f** orbital

First Orbit (K and n = 1)

Angular Momentum Number (l) = 0 to (1 – 1) = 0 (0 to 0)

Which means first orbit just have one subshell which is **s**

Second Orbit (L and n = 2)

Angular Momentum Number (l) = 0 to (2 – 1) = 1 (0 to 1)

Which means second orbit have two subshells which are **s** and **p**

Third Orbit (M and n = 3)

Angular Momentum Number (l) = 0 to (3 – 1) = 2 (0 to 2)

Which means third orbit have three subshells (0, 1, 2) which are **s**, **p** and **d**

Fourth Orbit (N and n = 4)

Angular Momentum Number (l) = 0 to (4 – 1) = 3 (0 to 3)

Which means fourth orbit have four subshells (0, 1, 2, 3) which are **s**, **p**, **d** and **f**

Orbit | Principle Quantum Number | Number of Subshells | Subshells |
---|---|---|---|

First Orbit (K) | n = 1 | 1 | 1s |

Second Orbit (L) | n = 2 | 2 | 2s 2p |

Third Orbit (M) | n = 3 | 3 | 3s 3p 3d |

Fourth Orbit (N) | n = 4 | 4 | 4s 4p 4d 4f |

These s, p, d and f subshells further have subregions which are called Orbitals, orbitals are just regions inside a subshell where probability of existence of an electron is quite high.

How many orbitals a subshell have depends upon it’s Angular Momentum Number (l) and can be calculated using formula.

Number of orbitals in a subshell = **2l + 1** where I is Angular Momentum Number of a subshell.

Therefore

s subshell (Angular Momentum Number l = 0)

Number of orbitals = 2(0) + 1 = 1

So s subshell just have one orbital

p subshell (Angular Momentum Number l = 1)

Number of orbitals = 2(1) + 1 = 3

So p subshell have three orbitals

d subshell (Angular Momentum Number l = 2)

Number of orbitals = 2(2) + 1 = 4 + 1 = 5

so d subshell have five orbitals

f subshell (Angular Momentum Number l = 3)

Number of orbitals = 2(3) + 1 = 6 + 1 = 7

so f subshell have seven orbitals

Moreover electron holding capacity of a subshell can be calculated using formula

Number of electrons which a subshell can hold = 2(2I + 1) where I is Angular Momentum Number of subshell

Therefore

s subshell (Angular Momentum Number l = 0)

Number of electrons it can hold = 2(2(0) + 1) = 2(1) = 2

So s subshell can hold maximum two electrons

p subshell (Angular Momentum Number l = 1)

Number of electrons it can hold = 2(2(1) + 1) = 2(3) = 6

So p subshell can hold maximum six electrons

d subshell (Angular Momentum Number l = 2)

Number of electrons it can hold = 2(2(2) + 1) = 2(4 + 1) = 2(5) = 10

so d subshell can hold maximum ten electrons

f subshell (Angular Momentum Number l = 3)

Number of electrons it can hold = 2(2(3) + 1) = 2(6 + 1) = 2(7) = 14

so f subshell can hold maximum fourteen electrons

Subshell | Angular Momentum Number (I) | Number of Orbitals in Subshell (2l + 1) | Maximum Electrons Subshell can hold 2(2l + 1) |
---|---|---|---|

s | 0 | 1 | 2 |

p | 1 | 3 | 6 |

d | 2 | 5 | 10 |

f | 3 | 7 | 14 |

Summarising all this we can write energy levels in an atom as

1s

2s 2p

3s 3p 3d

4s 4p 4d 4f

5s 5p 5d 5f 5g

But next question which arises is “in which order these orbitals should be filled in to figure out electron configuration of an atom?”.

Like should 2 electrons be filled in 1s orbital first or 3p orbital first???

Well answer to this question is **Aufbau Principle**.

According to the Aufbau Principle, in the ground state of an ion or an atom, electrons first occupy the atomic orbitals of lowest energy levels before filling up in higher energy levels. What this indicates is that the orbital with the lower energy will be filled first, followed by the orbital with the greater energy.

As per this principle energy of any orbital depends upon sum of Principle Quantum Number (n) and Angular Quantum Number (l).

Therefore

Energy of Orbital = n + l

So lower the value of n + l is lower its energy.

Orbital | n | I | Energy (n + l) |
---|---|---|---|

1s | 1 | 0 | 1 |

2s | 2 | 0 | 2 |

2p | 2 | 1 | 3 |

3s | 3 | 0 | 3 |

3p | 3 | 1 | 4 |

3d | 3 | 2 | 6 |

4s | 4 | 0 | 4 |

4p | 4 | 1 | 5 |

4d | 4 | 2 | 6 |

4f | 4 | 3 | 7 |

From the above table its clear that 4s have less energy than 3d, so it should be filled first.

Based upon the energies of orbitals as per Aufbau Principle, order of filling of orbitals is **1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 8s** and so on.

It’s tricky to remember what’s order of filling of orbitals as per Aufbau Principle, so you can use below diagram for easily filling up orbitals. Just follow the arrows from top right corner to bottom left corner diagonally.

Order of filling of orbitals as per Aufbau Principle is **1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 8s** and so on.

**As Beryllium atom have four electrons, therefore it’s electron configuration is 1s ^{2} 2s^{2}. Which means Beryllium atom have 2 electrons each in its 1s and 2s orbitals.**

## Valence Electrons of Beryllium (Be)

Number of electrons in the last orbit of an element’s atom are called valence electrons.

As Beryllium (Be) have electron configuration **1s ^{2} 2s^{2}** so it’s last orbit is 2 (L shell which have Principle Quantum Number n = 2), as last orbit of Beryllium have 2 electrons, therefore

**number of valence electrons in Beryllium (Be) is two**.

Beryllium (Be) | 2 valence electron |

### How many Valence Electrons does Beryllium have?

Beryllium has 4 electrons so it’s Orbital Electron Configuration is 1s^{1} 2s^{2}. As electron configuration shows, Beryllium have **2 valence electrons** located in 2s subshell orbital.

### Does Beryllium have 4 valence electrons?

As Beryllium (Be) have electron configuration **1s ^{2} 2s^{2}** and number of electrons in the last orbit of an element’s atom are called valence electrons. Therefore Beryllium just have 2 valence electrons in 2s subshell and not 4 valence electrons.

### Why Beryllium lose 2 electrons?

Beryllium have electron configuration **1s ^{2} 2s^{2}**, there are 2 electrons in 2s subshell but if Beryllium looses both of these two electrons. Then electron configuration becomes 1s

^{2}which is electron configuration of Helium, a noble gas and therefore is more stable as compared to electron configuration of Beryllium (1s

^{2}2s

^{2}).

Thus in order to become more stable, Beryllium easily looses 2 electrons and achieve more stable electron configuration of Helium.

## Valency of Beryllium (Be)

Valency refers to the ability of an element to combine with other elements. Valencies are same throughout the periodic table for elements that are located in the same group.

Which means valency is same for all of Group 1 elements (K, Na etc. have valency = 1), Group 2 elements (Ca, Mg etc. have valency = 2) and so on for other groups in the periodic table. Also valency depends upon number of electrons that are found in an element’s outer most shell.

As Beryllium (Be) have electron configuration **1s ^{2} 2s^{2}**, which means both orbitals inside 1s and 2s subshells are fully filled.

Therefore Be atom is not stable and want to loose two electrons in its 2s orbital and achieve more stable electron configuration **1s ^{1}**.

**Therefore valency of Beryllium (Be) is two.**

Beryllium (Be) | Valency = 2 |

### Does Beryllium have Valency 2?

Valency refers to the ability of an element to combine with other elements and depends upon number of electrons available in most outermost shell of atom.

Beryllium atom has two shells K and L. Both of which are fully filled with 2 electrons. Therefore Beryllium can loose two electrons to gain fully stable electron configuration of Helium (having 2 electrons in K shell).

As Beryllium can loose two electrons to become more stable, therefore **it’s valency is two**.

### How is valency of Beryllium 4?

No based upon Electron Configuration of Beryllium **1s ^{2} 2s^{2}** it have valency 2, not 4.

## Beryllium (Be^{2+}) Electron Configuration

Above I discussed that in order to achieve stable electron configuration, in which all of orbitals are fully filled with electrons. Beryllium want to loose its two electrons in 2s orbital. But when an atom of Beryllium does loose two electrons, then number of protons(positive charge) and number of electrons(negative charge) becomes unequal.

Thus forming a Beryllium (Be^{2+}) ion.

Be → Be^{2+} + 2e^{–}

So Orbital Electron Configuration of Beryllium (Be) atom is **1s ^{2} 2s^{2}** and after loosing two electrons it becomes

**1s**.

^{2}Therefore Electron Configuration of Beryllium (Be

^{2+}) ion is

**1s**.

^{2}## FAQs

**What is electron configuration of neutral Beryllium?**

Neutral Beryllium atom means that it have equal number of electrons and protons. As in neutral state beryllium atom have total four electrons, therefore it’s electron configuration is 1s^{2} 2s^{2}. Which means beryllium atom have 2 electrons each in its 1s, 2s orbitals.

**What is electron configuration of ground-state Beryllium atom?**

Ground state atom means that all electrons inside it are in least possible energy state levels, therefore net total energy of atom in ground-state is minimum out of all possible states of it. As beryllium atom just have 4 electrons, therefore it’s electron configuration is 1s^{2} 2s^{2}. Which means beryllium atom have 2 electrons each in its 1s, 2s orbitals.

**What is electron configuration of Be(2+) ion?**

When an atom of beryllium loose 2 electrons, then number of protons(positive charge) and number of electrons(negative charge) becomes unequal. Thus forming a beryllium ion (Be^{2+}). As electron configuration of beryllium atom is 1s^{2} 2s^{2} and formation of beryllium ion (Be^{2+}) require loosing of 2 electrons therefore **electron configuration of beryllium ion is 1s ^{2}**.

**Which element have electron configuration 1s**

^{2}2s^{2}?Beryllium (Be)

**In what type of orbital is the outermost electron in Beryllium?**

Electron configuration of beryllium is 1s^{2} 2s^{2}

From this it can be clearly observed that outermost electron in beryllium atom is present in **2s orbital**.

## Some Properties of Beryllium

Element Name | Beryllium |

Symbol | Be |

Atomic Number | 4 |

Number of electrons | 4 |

Group in Periodic Table | 2 |

Atomic Weight | 9.012138 u |

Number of Valence Electrons | 2 |

Valency | 2 |

First Ionisation Energy | 899.5 kJ/mol |

Second Ionisation Energy | 1757.1 kJ/mol |

Third Ionisation Energy | 14,848.7 kJ/mol |

Oxidation State | 2 |

Melting Point | 1560 K |

Boiling Point | 2742 K |

Atomic Radius | 112 picometer |

Electronegativity | 1.57 eV |

Covalent Radius | 96 ± 3 picometer |

Van der waals Radius | 153 picometer |