chapter 6

Question 1

compound

Answer 1

• a pure substance
• made of two or more different elements
  that are chemically combined

2 types of compounds:
1) ionic compound
2) molecular compound

Question 2

chemical bond

Answer 2

• a chemical link between two atoms,
  which holds the atoms together

2 types of chemical bonds:

1) ionic bond
2) covalent bond

Question 3

Recall

Answer 3

– a full outer energy level contains 8 electrons (like
the noble gases)
– a full outer energy level provides more chemical
stability / less reactivity
– atoms can achieve a full outer energy level by
gaining, losing, or sharing electrons with another
atom during a chemical reaction

Question 4

Reactivity

Answer 4

• an element is stable when it has 8 electrons in
  the outer shell (octet rule)
  – except hydrogen (H), helium (He), lithium (Li) and
  beryllium (Be) which are stable with 2 electrons in the
  outer shell

Question 5

Reactivity 2

Answer 5

• The closer to a full electron shell an atom is,
  the more reactive it is
  – more reactive means the atom is more likely to
  take part in a chemical reaction to form a
  compound
  – less reactive means the atom is less likely to take
  part in a chemical reaction to form a compound

Question 6

Ions

Answer 6

• When atoms lose or gain electrons, they
  become ions.
  – **Cations **are positive and are formed by elements
  on the left side of the periodic chart (metals).
  – Anions are negative and are formed by elements
  on the right side of the periodic chart (non-metals).
  – Hydrogen is unique due to its 1 valence electron
  (can form a cation or an anion).

Question 7

ion charge=

Answer 7

protons + electrons

Question 8

ions charges examples

Answer 8

eg.lithium atom:3 protons 3 electrons 0charge
loss of electrons=(lithum ion)3protons 2electrons 1+ charge
* e.g. sodium ion has 11 protons (+11) and 10
electrons (-10) for a charge of +1, represented
as Na+

Question 9

Halogens (group 17)

Answer 9

➢ all atoms have 7 valence electrons.
➢ need to gain 1 electron to have a
stable octet.
➢ form anions.
➢ Ions will have a charge of 1-.

Question 10

Alkali Metals (group 1)

Answer 10

➢ all atoms have 1 valence electron.
➢ need to lose 1 electron to have a
stable octet.
➢ form cations.
➢ Ions will have a charge of 1+.

Question 11

Alkaline Earth Metals (group 2) .

Answer 11

➢ all atoms have 2 valence electrons.
➢ need to lose 2 electrons to have a
stable octet.
➢ form cations
➢ Ions will have a charge of 2+,

Question 12

Ionic Compounds

Answer 12

When an ionic compound forms, the metal
atom donates its valence electrons to the
non-metal atom in order for both atoms
to form a stable octet.
Example: sodium and chlorine combine
to form sodium chloride, NaCl
An ionic bond involves the transfer of one or
more electrons.

Remember: Metals are electron donors.
Non-metals are electron acceptors.

Question 13

Ionic Bonds

Answer 13

Ionic compounds (such as NaCl) are
generally formed between metals and
nonmetals.

Question 14

Ionic bond

Answer 14

• a chemical bond that forms by
  the attraction between
  oppositely charged ions
  (electrostatic forces)
• Involves a transfer of electrons:
  (Metals are electron donors;
  non-metals are electron
  acceptors.
• strong but weaker than
  covalent bonds
• require a lot of energy to break

Question 15

Drawing BR diagrams for ionic compound

Answer 15

• Magnesium loses 2
  electrons for an ionic
  charge of 2+
• Oxygen gains 2 electrons
  for an ionic charge of 2-
• Remember the ionic
  charges should cancel out
  to leave the ionic
  compound neutral (NO
  charge).
• See BLM 6-5 and your
  textbook for additional
  examples.

magnesium oxide, MgO

Don’t forget to draw the nucleus
correctly with protons and neutrons.

Question 16

Properties of Ionic Compounds

Answer 16

• Physical States
• Solubility
• Conductivity

Question 17

1. 1) Physical States

Answer 17

• solid
  – each ion strongly attracted to ions around it
• crystal lattice
  – regular, repeating
  pattern of ions
• high melting point
  – lots of energy is needed to break ionic bond
  – e.g. mpNaCl = 801oC
  1) Physical States

Question 18

2) Solubility

Answer 18

• soluble in water
  – water separates positive
  and negative ions from
  each other, causing ionic
  bonds to break
  – ions in solution are able
  to move around

Question 19

Solubility

Answer 19

• human body is an
  aqueous (water)
  environment that
  contains dissolved ions
  for vital processes
• e.g.
  – Na+ and K+

transmission of

nerve impulses and
control of muscular
contractions,
– CO3

2- blood

• dehydration – water and
  essential ions are lost

Question 20

Conductivity

Answer 20

• good conductors as liquid (poor conductors as solid)
  – in liquid charged particles (e.g. electrons or ions) are free to move around
  – in solid ions are locked into position in crystal lattice

Question 21

Writing Formulas

Answer 21

• Because compounds are electrically neutral, one can determine the formula of a compound this way:
  – The charge on the cation becomes the subscript on the anion.
  – The charge on the anion becomes the subscript on the cation.
  – Criss-cross or cross-over method.
  – If these subscripts are not in the lowest whole-
  number ratio, divide them by the greatest common
  and Ions
  factor – always write in lowest terms!! Atoms, Molecules,
  – Never write a subscript of “1”

Question 22

In solution

Answer 22

conductivity

Question 23

In solid

Answer 23

unconductable