Chemical Changes And Structure

Question 1

groups

Answer 1

vertical columns within the table which contains elements with similar chemical properties resulting from a common number of electrons in the outer shell

Question 2

periods

Answer 2

rows of elements arranged with increasing atomic number, demonstrating an increasing number of outer electrons and a move from metallic to non-metallic characteristics

Question 3

what are the different types of structures

Answer 3

metallic, covalent molecular, covalent network, monatomic

Question 4

what is covalent radius

Answer 4

a measure of the size of atom

Question 5

how can the trends in covalent radius across periods and down groups be explained in terms of

Answer 5

the number of occupied shells, and the nuclear charge

Question 6

what is first ionisation energy

Answer 6

the energy required to remove one mole of electrons from one mole of gaseous atoms

Question 7

what are second, third, fourth etc. ionisation energies

Answer 7

the energies required to remove further moles of electrons

Question 8

what can trends in ionisation energies across periods and down the groups be explained in terms of?

Answer 8

the atomic size, nuclear charge and the screening effect due to inner shell electrons

Question 9

electronegativity

Answer 9

a measure of the attraction an atom involved in a bond has for the electrons of the bond

Question 10

what happens in covalent bonds

Answer 10

atoms share pairs of electrons

Question 11

what is a covalent bon a result of

Answer 11

two positive nuclei being held together by their common attraction for the shared pair of electrons

Question 12

how are polar covalent bonds formed

Answer 12

when the attraction of the atoms for the pair of bonding electrons is different

Question 13

what are ionic bonds

Answer 13

the electrostatic attraction between positive and negative ions

Question 14

what do ionic compounds form

Answer 14

lattice structures of oppositely charged ions

Question 15

what can pure covalent bonding and ionic bonding be considered as

Answer 15

opposite ends of a bonding continuum, with polar covalent lying between these two extremes

Question 16

what happens if the difference in electronegativities between the bonded atoms is large

Answer 16

the more polar it will be and then the movement of bonding electrons from the element of lower electronegativity to the element of higher electronegativity is complete, which results in the formation of ions

Question 17

what are the intermolecular forces acting between molecules known as

Answer 17

Van Der Waals forces

Question 18

what are the types of intermolecular forces

Answer 18

london dispersion forces and permanent dipole-permanent dipole interactions that include hydrogen bonding

Question 19

what are london dispersion forces

Answer 19

forces of attraction that can operate between all atoms and molecules, they are much weaker than all other types of bonding

Question 20

how are london dispersion forces formed

Answer 20

they are formed as a result of electrostatic attraction between temporary dipoles and induced dipoles caused by the movement of electrons in atoms and molecules

Question 21

what is the strength of london dispersion forces related to

Answer 21

the number of electrons within an atom or molecule

Question 22

what is a molecule described as if it has a permanent dipole

Answer 22

polar

Question 23

what atoms of what elements are there hydrogen bonds between the atoms present

Answer 23

strongly electronegative elements such as fluorine, oxygen and nitrogen, which are highly polar

Question 24

what are hydrogen bonds

Answer 24

electrostatic forces of attraction between molecules that contain these highly polar bonds. They are stronger than other forms of permanent dipole-permanent dipole interaction but weaker than a covalent bond

Question 25

what are differences in the boiling points and melting points of polar substances and non-polar substances with similar numbers of electrons

Answer 25

the melting points and boiling points of polar substances are higher than the boiling points and melting points of non-polar substances

Question 26

what properties of substances are affected by hydrogen bonding

Answer 26

boiling points, melting points, viscosity and solubility/miscibility in water

Question 27

what does hydrogen bonding between molecules in ice result in

Answer 27

an expanded structure that causes the density of ice to be less than that of water at low temperatures

Question 28

what do ionic compounds and polar molecules tend to be soluble in

Answer 28

polar solvents such as water

Question 29

what do ionic compounds and polar molecules tend to be insoluble in

Answer 29

non-polar solvents

Question 30

what do non-polar molecular substances tend to be soluble and insoluble in

Answer 30

soluble in non-polar solvents and insoluble in polar solvents

Question 31

where do pure covalent bonds exist between

Answer 31

atoms with the same electronegativities and the electrons are shared evenly and the molecule has no ionic character

Question 32

what are polar covalent molecules known as

Answer 32

dipoles

Question 33

when do polar covalent bonds arise

Answer 33

when atoms do not share their pair of electrons equally

Question 34

what happens during pure covalent bonding

Answer 34

atoms with higher electronegativities pull the shared pair of electrons closer

Question 35

what are london dispersion forces caused by

Answer 35

the temporary uneven distribution of electrons within atoms forming temporary dipoles

Question 36

what happens to the atom with the higher electronegativity in ionic bonds

Answer 36

it pulls the shared electrons towards itself completely forming a negative ion

Question 37

what happens to the atom with the lower electronegativity in ionic bonds

Answer 37

it loses its bonding electron to form a positive ion

Question 38

properties of ionic compounds

Answer 38

they form ionic lattices with high melting and boiling points

Question 39

why do polar substances have higher melting point and boiling points compared to non-polar substances

Answer 39

because the molecules are more difficult to seperate

Question 40

what type of attraction is found in metallic bonding

Answer 40

an electrostatic attraction between the positive metal ions and the delocalised electrons

Question 41

why are metal elements good conductors of electricity

Answer 41

because the have delocalised electrons

Question 42

what are discrete covalent molecules held together by

Answer 42

strong covalent bonds between atoms and weak intermolecular forces between molecules

Question 43

what are the covalent molecular elements

Answer 43

chlorine, fluorine, oxygen, nitrogen, hydrogen, sulfur and carbon in the form of fullerenes

Question 44

what are covalent networks held together by

Answer 44

strong covalent bonds

Question 45

what are monoatomic elements

Answer 45

stable atoms with full outer energy levels so they do not usually form molecules with other atoms

Question 46

characteristics of monatomic elements

Answer 46

low melting and boiling points because it is easy to overcome the weak intermolecular forces between the atoms

Question 47

what happens to the ionisation energy as you move across a period from left to right

Answer 47

it increases as the atoms have more protons in the nucleus so outer electrons are harder to remove

Question 48

what happens to the ionisation energy as yo move down a group

Answer 48

it decreases because the outer electrons are further away from the nucleus and shielded by the full inner shells of electrons, and are easier to remove

Question 49

what happens to the electronegativity as you move across a period from left to right

Answer 49

it increases as the atoms have more protons in their nuclei which increases their effective nuclear charge and attracting bonding electrons more strongly

Question 50

what happens to the electronegativity as you move down a group in the periodic table

Answer 50

it decreases as you have more energy levels so the nuclei are further away from the bonding electrons and shielded from it

Question 51

what is the rate of a chemical reaction proportional to

Answer 51

the concentration of reactants present

Question 52

what happens as a reaction proceeds

Answer 52

the concentration of the reactants decreases which results in a decrease in the rate of the reaction

Question 53

activation energy

Answer 53

the minimum kinetic energy required for a reaction

Question 54

why must must reactant molecules have enough energy to collide

Answer 54

so that they can overcome the repulsive forces

Question 55

activated complex

Answer 55

high energy intermediate state where bonds are breaking and forming

Question 56

what must happen in order for an activated complex to be formed

Answer 56

collision of molecules with the correct geometry \

Question 57

what are the four factors that affect how reactant molecules collide

Answer 57

temperature, concentration, particle size, catalyst

Question 58

what do catalysts do

Answer 58

they reduce the activation energy of the reaction by providing a lower energy pathway

Question 59

what affect does increasing temperature have on kinetic energy

Answer 59

the number of particles with kinetic energy above the activation energy increases

Question 60

enthalpy change

Answer 60

the difference in energy between reactants and products

Question 61

what do potential energy diagrams show

Answer 61

the progress of a reaction from reactants to products