Lewis Dot Structures Of Atoms And Ions Worksheet (Page 3 of 5) in pdf

Lewis Dot Structures Of Atoms And Ions Worksheet Page 3

Topic H – Bonding – 01

Block 071

Lewis Dot Structures of Atoms and Ions

PDP Chemistry

Page 3 of 5

Noble gases are unreactive in chemical reactions. This is because they have a very stable

electron configuration. All noble gases (except helium) have a general electron

configuration of ns

, or eight valence electrons. In forming compounds, other atoms

tend to achieve the electron configuration of a noble gas. Anions get a negative charge

when they gain electrons to get eight valence electrons. Cations get a positive charge

when they lose electrons to end up with eight electrons. This tendency for an atom to end

up with eight electrons is called the octet rule.

Anions: The element fluorine has nine electrons. It has an electron configuration of

. Since the highest occupied energy level is 2, we can determine that fluorine

has seven valence electrons (s

). To become like a noble gas, fluorine can do one of two

things. It can lose seven valence electrons to become like helium, the previous noble gas.

Or, it can gain one valence electron to become like neon, the next noble gas. It is easier for

an atom to gain one electron than it is to lose seven, so fluorine achieves noble gas

configuration by gaining one valence electron. The dot structure for an anion looks like

this:

→

A fluorine atom gains one electron to become a negatively charged fluoride ion.

Almost all negatively charged ions have eight valence electrons, because almost all noble gases have eight

valence electrons. The brackets and charge must always be included when drawing the electron dot

configuration for an ion.

Cations: While it is easier for atoms on the right

side of the periodic table to achieve noble gas

configurations by gaining electrons, the opposite

is true of atoms from the left side of the table.

An atom like sodium has 11 electrons, and a

configuration of 1s

. This means that

is only has one valence electron. It is easier for

sodium to become like a noble gas by giving up

one electron to become like neon than it is to

gain seven electrons to become like argon.

Lewis Dot Structures Of Atoms And Ions Worksheet Page 3