9th grade atoms, elements and the periodic table

Example

How many electrons does an atom of neon (atomic number 10) have in its outer shell?

1. 2,8
2. So the answer is: 8

Answer: 8

Example

Phosphorus (P) is in group 15 (5). What charge does its ion have?

1. It gains 3 electrons, so the ion is negative.
2. So the answer is: 3−

Answer: 3−

Example

What is the formula of potassium sulfate? (Ions: K⁺ and SO₄²⁻)

1. 2 × (+1) and 1 × (−2) give zero overall charge.
2. So the answer is: K₂SO₄

Answer: K₂SO₄