Atomic Structure

Rules Of Atomic Structure

1. The Number of electrons = number of protons

2. Atomic Number = the number of protons/electrons

3. Atomic Mass = number of protons or electrons + number of neutrons

• Group number is same number of electrons in outer shell

• Period number = number of shells

• 1st Shell holds 2 electrons

• 2nd Shell holds 8 electrons

• 3rd Shell holds 8 electrons

Drawing Atoms

Hydrogen (H)

Hydrogen has an Atomic number of 1, it is in group 1 and it is in period 1.

So Hydrogen has:

1 shell containing 1 electron in the outer shell. It has a total of 1 electron

Helium (He)

Helium has an Atomic number 2, it is in group 0 and it is in period 1.

So helium has:

1 shell containing 2 electrons. It has a total of 2 electrons.

Lithium (Li)

Lithium has an Atomic number 3, it is in group 1 and it is in period 2.

So Lithium has:

2 shells with 1 electron in the outer shell. It has a total of 3 electrons. Its electron arrangement is 2,1

Beryllium (Be)

Beryllium has an Atomic number 4, it is in group 2 and it is in period 2.

So helium has:

2 shells with 2 electrons in the outer shell. It has a total of 4 electrons. Its electron arrangement is 2,2

Boron (B)

Boron has an Atomic number 5, it is in group 3 and it is in period 2.

So Boron has:

2 shells with 3 electrons in the outer shell. It has a total of 5 electrons. Its electron arrangement is 2,3

Carbon (C)

Carbon has an Atomic number 6, it is in group 4 and it is in period 2.

So Carbon has:

2 shells with 4 electrons in the outer shell. It has a total of 6 electrons. Its electron arrangement is 2,4

Nitrogen (N)

Nitrogen has an Atomic number 7, it is in group 5 and it is in period 2.

So Nitrogen has:

2 shells with 5 electrons in the outer shell. It has a total of 7 electrons. Its electron arrangement is 2,5

Oxygen (O)

Oxygen has an Atomic number 8, it is in group 6 and it is in period 2.

So Oxygen has:

2 shells with 6 electrons in the outer shell. It has a total of 8 electrons. Its electron arrangement is 2,6

Fluorine (Fl)

Fluorine has an Atomic number 9, it is in group 7 and it is in period 2.

So Fluorine has:

2 shells with 7 electrons in the outer shell. It has a total of 9 electrons. Its electron arrangement is 2,7

Neon (Ne)

Neon has an Atomic number 10, it is in group 0 and it is in period 2.

So Neon has:

2 shells with 8 electrons in the outer shell. It has a total of 10 electrons. Its electron arrangement is 2,8

Sodium (Na)

Sodium has an Atomic number 11, it is in group 1 and it is in period 3.

So Sodium has:

3 shells with 1 electrons in the outer shell. It has a total of 11 electrons. Its electron arrangement is 2,8,1

Magnesium (Mg)

Magnesium has an Atomic number 12, it is in group 2 and it is in period 3.

So Magnesium has:

3 shells with 2 electrons in the outer shell. It has a total of 12 electrons. Its electron arrangement is 2,8,2

Aluminium (Al)

Aluminium has an Atomic number 13, it is in group 3 and it is in period 3.

So Aluminium has:

3 shells with 3 electrons in the outer shell. It has a total of 13 electrons. Its electron arrangement is 2,8,3

Silicon (Si)

Silicon has an Atomic number 14, it is in group 4 and it is in period 3.

So Silicon has:

3 shells with 4 electrons in the outer shell. It has a total of 14 electrons. Its electron arrangement is 2,8,4

Phosphorus (P)

Phosphorus has an Atomic number 15, it is in group 5 and it is in period 3.

So Phosphorus has:

3 shells with 5 electrons in the outer shell. It has a total of 15 electrons. Its electron arrangement is 2,8,5

Sulphur (S)

Sulphur has an Atomic number 16, it is in group 6 and it is in period 3.

So Sulphur has:

3 shells with 6 electrons in the outer shell. It has a total of 16 electrons. Its electron arrangement is 2,8,6

Chlorine (Cl)

Chlorine has an Atomic number 17, it is in group 7 and it is in period 3.

So Chlorine has:

3 shells with 7 electrons in the outer shell. It has a total of 17 electrons. Its electron arrangement is 2,8,7

Argon (Ar)

Argon has an Atomic number 18, it is in group 0 and it is in period 3.

So Sodium has:

3 shells with 8 electrons in the outer shell. It has a total of 18 electrons. Its electron arrangement is 2,8,8

Potassium (K)

Potassium has an Atomic number 19, it is in group 1 and it is in period 4.

So Potassium has:

4 shells with 1 electron in the outer shell. It has a total of 19 electrons. Its electron arrangement is 2,8,8,1

Calcium (Ca)

Calcium has an Atomic number 20, it is in group 2 and it is in period 4.

So Sodium has:

4 shells with 2 electrons in the outer shell. It has a total of 20 electrons. Its electron arrangement is 2,8,8,2

Questions

1. What is the atomic structure of Boron?2. Draw and oxygen atom

i. How many electrons are there in the outer shell?ii. How many electrons does oxygen atom?

3. An atom has 2 shells and 3 electrons, what atom is this?

4. Which atom is group 4 and has 2 shells?