UNIT 1 : Bonding

Question 1

why do atoms form bonds?

Answer 1

Atoms form bonds to achieve a stable electron arrangement like the Noble gases

Question 2

when does a covalent bond form?

Answer 2

The covalent bond forms when 2 non-metal atoms share a pair of electrons

Question 3

what is a molecule?

Answer 3

A small group of atoms held together by covalent bonds

Question 4

what holds the atoms together in a covalent bond?

Answer 4

The forces of attraction between the positive nuclei of both atoms and the electrons in the overlap region holds the atoms together

Question 5

why are covalent bonds difficult to break?

Answer 5

A lot of energy is required to overcome forces of attraction, covalent bonds are very strong

Question 6

what are the two types of covalent bonds?

Answer 6

• covalent molecular substance

- covalent network substance

Question 7

what are the properties of a covalent molecular substance?

Answer 7

• low melting and boiling points as there are weak forces of attraction between the molecules ( intermolecular forces)
• weak intermolecular forces in between molecules
• strong covalent bonds

Question 8

what are properties of a covalent network substance?

Answer 8

• very high melting and boiling points due to strong covalent bonds
• solid at room temperature due to covalent bonds

Question 9

what are examples of a covalent network substance?

Answer 9

• Silicon dioxide

- Diamond

Question 10

what can an electron sharing diagram be used to show?

Answer 10

used to show the sharing of electron pairs that make up covalent bonds

Question 11

what are the seven diatomic elements?

Answer 11

• I BRing CLay For Our New House =

iodine, bromine, chlorine, fluorine, oxygen, nitrogen, hydrogen

Question 12

what are the properties of diatomic elements?

Answer 12

• weak intermolecular forces of attraction therefore low melting and boiling points
• held together with covalent bonds
• naturally exist as molecules with 2 atoms joined together

Question 13

what are the chemical formula for diatomic elements?

Answer 13

• iodine = I₂
• bromine = Br₂
• chlorine = Cl₂
• flourine = F₂
• oxygen = O₂
• nitrogen = N₂
• hydrogen = H₂

Question 14

what happens when hydrogen, fluorine, chlorine, bromine, iodine join together?

Answer 14

Form single covalent bonds

Question 15

what happens when oxygen joins together?

Answer 15

forms a double covalent bond

Question 16

what happens when nitrogen joins together?

Answer 16

forms a triple covalent bond

Question 17

what is the difference between the chemical formula and full structural formula?

Answer 17

The chemical formula only tells us the number of atoms and doesn’t give us any indication about the shape

Question 18

what are the different shapes of molecules?

Answer 18

• atoms arranged in a straight line are linear shaped
  e.g hydrogen chloride H—Cl
• two dimensional are angular shaped O
  e.g water , H₂o / \
  H H
• three dimensional - trigonal pyramidal and tetrahedral
  e.g nitrogen hydride

Question 19

what is meant by an ion?

Answer 19

An ion is a positively or negatively charged element?

Question 20

what is meant by an iconic bond?

Answer 20

An ionic bond is the electrostatic attraction between positive and negative ion

Question 21

what is meant by an iconic compound?

Answer 21

An iconic compound is made up of both metal ions ( positively charged) and non- metals ( negatively charged) ions.

Question 22

what is meant by crystal lattice?

Answer 22

A crystal lattice is the arrangement of ions in a solid

Question 23

what charge do metal ions have?

Answer 23

One positive charge

Question 24

what charge do non-metal ions have?

Answer 24

A negative charge

Question 25

how do you figure out the charge of a metal ion?

Answer 25

it is the same as the group the element is in

Question 26

how do you work out the charge of a non-metal ion?

Answer 26

by subtracting the group number from 8

Question 27

how do u work out the charge for the nuclide notation: ions?

Answer 27

• positive ions have more protons than electrons
• negative ions have more electrons than protons
• the difference between protons and electrons shows the number of + or - charge

Question 28

what is meant by a conductor?

Answer 28

Conductors are elements or compounds which allow energy to pass through

Question 29

what is meant by a non-conductor?

Answer 29

non-conductors are elements or compounds which do not allow energy to pass

Question 30

why are electrodes made of carbon?

Answer 30

made of carbon because carbon conducts electricity

Question 31

what form of carbon is used in electrodes?

Answer 31

very unreactive form of graphite which also conducts electricity

Question 32

what are electrodes?

Answer 32

The terminals through which the electrical current enters and leaves the substance under test

Question 33

how do you know if an element conducts electricity?

Answer 33

• substance-element-metal = conducts electricity

- substance-compound-ionic-liquid solution = conducts electricity

Question 34

do covalent compounds conduct electricity?

Answer 34

no covalent compound other than graphite conducts electricity

Question 35

what are the properties of covalent compounds?

Answer 35

• they are made up of molecules
• do not have an overall charge
• covalent molecular substances do not conduct electricity because they do not have charged particles that are free to move
• do not conduct electricity ( except graphite)

Question 36

what are ionic compounds?

Answer 36

compounds that contain both a metal and a non-metal element

Question 37

Do ionic compounds conduct electricity when solid?

Answer 37

not when solid as they don’t have any free moving particles

Question 38

can solid ionic compounds conduct electricity when heated or dissolved?

Answer 38

• when dissolved particles become free to move so they can conduct electricity
• when heated ions become free to move so they also become conducts