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MARKING SCHEME - CHEMICAL BONDS

ACTIVITY ANSWERS

1 No.1 Inert, monoatomic, stable, duplet, arrangement

2 Chemical bonds

3 (i) ionic (ii) covalent , sharing

2 1 (i) donates, positive (ii) non-metal, negative

2(a)(b)

3 1 Electron arrangement of sodium atom is 2.1

A sodium atom donates one electron to achieve the stable electron

arrangement which is 2.8. Sodium ion, Na+ , is formed

Electron arrangement of chlorine atom is 2.8.7

Electron from sodium atom is transferred to a chlorine atom

A chlorine atom receives/gains electron from sodium atom to achievethe stable electron arrangement which is 2.8.8

Chloride ion, Cl- is formed

The sodium ion,+

Na and chloride ion,

Cl formed are attracted to

one another to form an ionic compound sodium chloride, NaCl .

The strong electrostatic forces between the opposite-charged ions iscalled ionic bond.

2 Refer to page 86 - F4 Chemistry text book for guidance3(a) Electron arrangement of magnesium atom is 2.8.2

A magnesium atom donates two electrons to achieve the stableelectron arrangement which is, 2.8.

Magnesium ion, Mg2+ is formed

Electron arrangement of chlorine atom is 2.8.7

Electrons from magnesium atom is transferred to two chlorine atoms

A chlorine atom receives/ gains electron from magnesium atom toachieve the stable electron arrangement which is 2.8.8.

Chloride ion, Cl- is formed

The magnesium ion,Mg2+ and two chloride ions,

Cl formed are

attracted to one another to form an ionic compound magnesiumchloride, MgCl2

The strong electrostatic forces between the opposite-charged ions iscalled ionicbond

(b) Refer to page 86 - F4 Chemistry text book

4 1 Non-metal, share, stable

2 (i) single bond ,(ii) double bond, (iii) triple bond

3 A pair, two pairs, three pairs

2-

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Atom W receives one electron from atom G to achieve the stableelectron arrangement which is 2.8.8

W ion, W- is formed

The G ion, G+ and W ion W- , formed are attracted to one another toform an ionic compound, GW

The strong electrostatic forces between the opposite-charged ions iscalled ionic bond.

Covalent bond

Atom E has fourvalence electrons, with an electron arrangement of2.4

It needs fourmore electrons to achieve the stable electron arrangement

One atom of E contributes 4 electrons forsharing

Atom W has seven valence electrons, with an electron arrangement of2.8.7

It needs one more electron to achieve the stable electron arrangement

One atom of E share a pair of electrons with fouratoms of W

Covalent compound ofEW4 is formed