Covalent Bonding Lewis dot structures

Covalent Bonding - Bohr

• Atoms overlap slightly, and one unpaired electron from each atom will pair together

• Both atoms are attracted to the same pair of electrons forming a covalent bond

1 shell

2 shells

3 shells

4 shells

COVALENT COMPOUNDS

• Covalent bonds form when electrons are shared between two nonmetals.

• Electrons stay with their atom but overlap with other shells.

• Ex. H2O

Shared electrons! Shared electrons!

BOHR DIAGRAMS OF COVALENT COMPOUNDS

Try it on your own!

•HF•NH3

•CH4

BOHR DIAGRAMS OF COVALENT COMPOUNDS

Bonding electrons are shared.• Examples: HF; NH3; CH4

WHAT IS A LEWIS DIAGRAM?

• Lewis diagrams represent the atom of an element by showing only the outer valance electrons and the chemical symbol.

Except for the transition elements (Groups 3–12), the lastdigit of the group number equals the number of e-s in thevalence shell.Examples:• Group 1 = 1 valence electron• Group 2 = 2 valence electrons• Group 13 = 3 valence electrons• Group 14 = 4 valance electrons• Group 15 = 5 valence electrons• Group 16 = 6 valence electrons• Group 17 = 7 valence electrons

WHAT IS A LEWIS DIAGRAM?

• Dots representing electrons are placed around element symbols at the points of the compass (north, east, south and west).

• Electron dots are placed singly first, until the 5th electron is reached and then they are paired.

LONE PAIRS AND BONDING ELECTRONS

• Pairs of electrons in Lewis Dot Diagrams are called LONE PAIRS.

• Single electrons are called BONDING ELECTRONS – because they are looking for another electron to bond with!

HOW MANY LONE PAIRS?

• Try it yourself!• Draw lewis dot structures for

– HF– NH3

– CH4

DIATOMICS – BECAUSE SOME ATOMS JUST CAN’T STAND TO BE ALONE

There are 7 diatomics:• iodine (I2)• bromine (Br2)• chlorine (Cl2)• fluorine (F2)• oxygen (O2)• nitrogen (N2)• hydrogen (H2)

IONIC COMPOUNDS

• Ionic bonds are formed when electrons are transferred from a metal ion (cation) to a non-metal ion (anion).

• Example: NaCl(s), FeCl2 (s)• Ionic Compounds are easy to recognize – they always contain a metal and a

nonmetal.