8.10 – Types of Bonds Chemical bond: force that holds atoms together to form molecules, the attraction between electrons of one atom to the nucleus of another atom The nature of the bond (degree of electron sharing) can be predicted using electronegativity

F Electronegativity: an atom’s ability to attract electrons e- I got cookies F e-

What happens when two atoms of the same element form a bond? No need to fight over us! We find you both equally attractive! HA HB e- e- 2.1 2.1

Covalent bonds occur between 2 non metals that have an electronegativity difference of ≤ 0.2 Equal sharing of electrons a pair of electrons is simultaneously attracted to two nuclei  two atoms share the bonding electrons atoms will try to get full outer shells

1 2.1 – 2.1 = 0 Example: hydrogen gas H2 How many bonds are there? ______(___________) Difference in electronegativity between the two atoms: _________________ single bond 2.1 – 2.1 = 0

Example: oxygen gas O2 3.5 3.5 2 How many bonds are there? _____ (_____________) Difference in electronegativity= _________________ double bond 3.5 – 3.5 = 0

How many electrons will be shared in a triple bond? 6

H Cl e- What happens when two different atoms form a bond? 2.1 3.0 Sorry H… but Cl is more attractive than you H Cl e- 2.1 3.0

Polar covalent bonds occur between 2 non-metals that have an electronegativity difference of 0.3 – 1.6 Unequal sharing of electrons a pair of electrons is shared, but they are more attracted to one nuclei than the other resulting in a __________________ dipole

.. d+ d- H : Cl : .. Example: HCl Let’s just look at the pair of electrons that are shared between H and Cl Electrons are more attracted to Cl because Cl has a higher electronegativity H becomes __________________________ Cl becomes __________________________ .. d+ d- H : Cl : .. 3.0 – 2.1 = 0.9 partially positively charged partially negatively charged

Example: H2O Again, let’s just look at the pair of electrons that are shared between H and O H becomes _______________________ O becomes _______________________ 3.5 – 2.1 = 1.4 d+ d+ H H O d- partially positively charged partially negatively charged

What happens when two atoms of very different electronegativities form a bond?

Ionic bonds occur between a metal and non-metal that have an electronegativity difference of > 1.6 No electron sharing, involves electron transfer 1+ 2+ 2- 1- 2+, 3+, 4+

Ionic bonds occur between a metal and non-metal that have an electronegativity difference of > 1.6 No electron sharing, involves electron transfer Metal atom (or the atom with lower electronegativity) gains electrons and becomes positively charged  cation Non-metal atom (or atom with the higher electronegativity) gains electrons and becomes negatively charged  anion Atoms are held together by ___________________

Atoms bonded covalently are held together by the sharing of electrons. No electron sharing occurs in ionic bonds. What is holding the two atoms together in an ionic bond?

Ionic bonds occur between a metal and non-metal that have an electronegativity difference of > 1.6 No electron sharing, involves electron transfer Metal atom (or the atom with lower electronegativity) gains electrons and becomes positively charged  cation Non-metal atom (or atom with the higher electronegativity) gains electrons and becomes negatively charged  anion Atoms are held together by ___________________ electrostatic charge

Example: NaF Difference in electronegativity between two atoms: 4.0 – 0.9 = 3.1