The importance of a full outer shellPart 11

When an atom gains or loses an electron it becomes an ION.

It now has either a positive or negative chargeNegative if it gains an electron -

AnionPositive if it loses an electron -

CationNon-metals gain electronsMetals lose electrons

Working out the charge:

16p-18e = -2

Oxygen has 8 protons

8 electrons + 2 = 10

8p – 10e = -2 4p-2e = +2

Ion Notation

Na1+Chemical symbol

Charge(1 electron lost)

How many electrons? Mg2+

p – e = charge12 – e = +212 = 2 + e12 – 2 = e e = 10

electrons

Mg2+Mg has 12

electrons if neutral

A charge of 2+ means it has lost 2 electrons

12 – 2 = 10

OR

Let’s practice

Cl has 17 protons- Charge = gain electron

17 + 1 = 18

7+3 = 10 13 – 3 = 10

Ca2+P3-

Give the ion notation for an atom with 11 protons and 10 electrons

Na1+