Ionic and Covalent Bonds - Mesa Public Schools · How do ionic bonds form? The bond is formed...

Ionic and

Covalent Bonds

Notes

Essential Question:

What are Ions and

how are they

formed?1

What areIons?

An ion is an atom (or group of atoms)

that has a positive or negative charge

Positive and negative ions are formed

when electrons are transferred (lost or

gained) between atoms

2

How do Metals form Ions? Metals tend to LOSE electrons, from their outer

energy level

a positively charged particle is called cation

The charge is written as a number followed by a

plus sign: Na1+

Now named a “sodium ion”

3

How do nonmetals for ions?

Nonmetals tend to GAIN one or more

electrons Negative ions are called anions

Cl1- is re-named a “chloride ion”

4

What are Polyatomic Ions?

Group of atoms that

act as a single unit that

have a charge

Example:

ammonium NH4+1

Carbonate CO3-2

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What are valence electrons?

The electrons in the outer energy

level, responsible for the chemical

properties of atoms.

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How do you find valence e-?

The number of valence electrons are easily

determined. It is the group number for

elements in group 1A to 8A

Li group 1A has 1 valance electron

N group 5 A has 5 valance electrons

Exception He only has 2 valance electrons

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Essential Questions

Why do atoms form bonds?

What is the difference between how an

ionic bond forms and a covalent bond

forms?

8

What is the octet rule?

When forming compounds atoms want a

stable electron configuration like a noble

gas. This means 8 electrons in the outer

most shell.

9

How do atoms become stable?

All atoms react to try and achieve a noble gas configuration.

8 valence electrons = already stable!

This is the octet rule (8 in the outer level is particularly stable).

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Ar

Electron Dots For CationsMetals will lose the valence electrons

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Ca

Electron Dots For Cations

Forming positive ions

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Ca2+NO DOTS are now shown for the cation.

This is named the

“calcium ion”.

Electron Dots For Anions

They will gain electrons to fill outer shell.

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P3-

(This is called the “phosphide

ion”, and should show dots)

What are bonds?Forces that hold groups of atoms together and

make them function as a unit.

What are the 3 types?

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1) Ionic bonds – transfer of electrons

2) Covalent bonds – sharing of

electrons.

3) Metallic bonds- “sea of electrons”

How do ionic bonds form?

The bond is formed through the transfer of electrons

(lose and gain)

Anions and cations are held together by opposite

charges (+ and -)

Usually a metal and nonmetal

Ionic compounds are called salts. Electrons are transferred to achieve noble gas

configuration.

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What properties do Ionic compounds

have?1. Crystalline solids - a regular repeating

arrangement of ions in the solid: Ions are

strongly bonded together.

Structure is rigid.

2. High melting points

3. Conduct electricity when dissolved in

water or melted (break apart into ions)

4. Brittle solids

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Ionic Bonding

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Na Cl

Ionic Bonding

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Na+ Cl -

Note: Remember that NO DOTS

are now shown for the cation!

Ionic solids are brittle

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+ - + -+- +-

+ - + -+- +-

Force

Ionic solids are brittle Strong Repulsion breaks a crystal apart,

due to similar ions being next to each

other.

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+- +-+ - + -

+- +-

Force

- Page 198

The ions are free to move when they are

molten (or in aqueous solution), and thus

they are able to conduct the electric current.

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How to read a formula

Ca3P2Formula

Shows the kinds and numbers of atoms in

the substance.

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How do covalent bonds form?

Always two or more non-

metals

Electrons are shared to hold

two atoms together in a bond.

Form molecules

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What are Diatomic Molecules?

A molecule made of 2 atoms

Memorize these 7 Br2, I2, N2,Cl2,

H2, O2, F2 “Dr. BrINClHOF”

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What are the properties of molecular

compounds?

lower melting and boiling points than ionic

compounds

tend to be gases or liquids at room

temperature

Do not break apart into ions when dissolved in

water stay in molecular form.

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Covalent bonding

Fluorine has seven valence electrons (but would like to have 8)

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F

Covalent bonding

Fluorine has seven valence electrons

A second atom also has seven

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F F

Covalent bonding

F F

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What are Metallic bonds?

How metal atoms are held

together in the solid.

Metals hold on to their valence

electrons very weakly.

Think of them as positive ions

(cations) floating in a SEA OF

ELECTRONS

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Sea of Electrons

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+ + + +

+ + + +

+ + + +

1) Ductility 2) Malleability

Due to the mobility of the

valence electrons, metals have:

and

Notice

that the

ionic

crystal

breaks

due to ion

repulsion!

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