Intro to Bonding

Valence Electrons, Lewis Dot Structures,

and Electronegativity

Standards2. Biological, chemical, and physical properties of matter result from the ability of atoms to form bonds from

electrostatic forces between electrons and protons and between atoms and molecules. As a basis for understanding this concept:

a. Students know atoms combine to form molecules by sharing electrons to form covalent or metallic bonds or by exchanging electrons to form ionic bonds.

2. b. Students know chemical bonds between atoms in molecules such as H2, CH4, NH3, H2CCH2, N2, Cl2, and many large biological molecules are covalent.

2. c. Students know salt crystals, such as NaCl, are repeating patterns of positive and negative ions held together by electrostatic attraction.

2. d. Students know the atoms and molecules in liquids move in a random pattern relative to one another because the intermolecular forces are too weak to hold the atoms or molecules in a solid form.

2. e. Students know how to draw Lewis dot structures.

2. f.* Students know how to predict the shape of simple molecules and their polarity from Lewis dot structures.

2. g.* Students know how electronegativity and ionization energy relate to bond formation.

2. h.* Students know how to identify solids and liquids held together by van der Waals forces or hydrogen bonding and relate these forces to volatility and boiling/melting point temperatures.

The Hippie

The Hippie

Sure man, it’s only money. I’ll probably be happier if I give it

away anyhow.

The Accountant

No Way am I giving you my Money!

You’re Irresponsible. In fact give me your

money so I can invest it for you!

The Accountant

Electronegativity

• electronegativity – how much an atom wants to keep hold of its electrons.

• ionization energy – the energy required to remove an electron from an atom.

Lower electronegativity

Greater electronegativity

Which has the greater electronegativity?

• Sodium or Oxygen? Oxygen

• Fluorine or Nitrogen?Fluorine

• Potassium or Iron?Iron

Lower ionization energy

Greater ionization energy

E.N. and I.E. increasing

Which has the greater ionization energy?

• Lithium or Beryllium? Beryllium

• Zinc or Calcium?Zinc

• Argon or Sulfur?Argon

Electronegativity vs. Ionization energy

• The greater the electronegativity, the more energy is needed to remove an electron.

• The lower the electronegativity, the less energy is needed to remove an electron.

Atomic Radii

• When atoms have greater electronegativity, they hold their electrons closer.

• Atoms with a lower electronegativity, have a greater atomic radius.

Atomic Radii

A.R. increasing

Reactivity

• The closer atoms are to the noble gases, the more they want to react so they can become like them.

More Reactive

More Reactive

A.R. increasing

More Reactive

E.N. and I.E. increasing

More Reactive

Ionic Radii

Compounds• Sometimes two (or more) different elements

encounter each other and the conditions are right to form a bond (or bonds) between them.

• This usually occurs because their electrons are more stable when they reorganize to form a bond.

• Often their electrons are organized more like a noble gases’ electrons after forming a compound.

• The group of two (or more) different elements are now called a compound.

Compounds

• bonds form between two different elements.

• Their electrons become more stable (often arranged more like a noble gases’ electrons).

• They are now called a compound.

Metals

Nonmetals

Three General Bonding Types

• Metal with Nonmetal

• Metal with Metal

• Nonmetal with Nonmetal

Nonmetals

Metals

Semi-metals or metalloids

Metal with Nonmetal Bonding

• Ionic compounds – the metal gives all of its valence electrons to the nonmetal.

• Known as – Salts, ions

Metal with Metal Bonding

• Metallic compounds – the both metals freely share their valence electrons with each other.

• Known as – alloys

Nonmetal with Nonmetal Bonding

• Covalent compounds – both nonmetals try to keep hold of their valence electrons as well as each other’s valence electrons. It ends up being a constant tug of war (although technically sharing).

• Known as – molecules

Three General Bonding Types

• Metal with Nonmetal- form ionic compounds

• Metal with Metal- form metallic compounds

• Nonmetal with Nonmetal- form covalent compounds

Three General Bonding Types• Metal with Nonmetal

- form ionic compounds (one gives, the other takes)

• Metal with Metal- form metallic compounds (both freely share

valence electrons - )

• Nonmetal with Nonmetal- form covalent compounds (both try to hold

on at the same time)

Nonmetals

Metals

Semi-metals or metalloids

Which kind of compound will these elements form?

• Iron and Nickel: Metallic compound

• Sulfur and Calcium:Ionic compound

• Carbon and Oxygen:Covalent compound

M + M metallicN + N covalentM + N ionic

Which kind of compound will these elements form?

• Hydrogen and Nitrogen: Covalent compound

• Magnesium and Oxygen:Ionic compound

• Gold and Zinc:Metallic compound

M + M metallicN + N covalentM + N ionic

Nonmetals

Metals

Semi-metals or metalloids

M + M metallicN + N covalentM + N ionic

NeFONCBBe

He

Li

H

Kr

ArCl

Br

XeI

SPSiMg Al

Ca

Na

K

4 e– in valence shell