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Chemistry H > U1 periodicity > Flashcards

U1 periodicity Flashcards

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1
Q

How are elements arranged on the periodic table?

A

In order of increasing atomic number

Groups:
-vertical columns
-contain elements if similar properties
-common number of electrons in outer shell

periods:
-rows of elements
-increasing atomic number
-increasing number of electrins
-move from metallic to non-metallic characteristics

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2
Q

What does the periodic table allow chemists to do?

A

make accurate predictions of physical properties and chemical behaviour for any element, based on its position

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3
Q

What is the atomic radius?

A

Distance from the centre of nucleus to outer electron shell

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4
Q

What is covalent radius?

A

half the distance between two nuclei in a bond. A measure of the size of an atom

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5
Q

What happens to atoms as you go down a group and why?

A

Get bigger:

-Greater number of electron shells
-Outer electrons not held as tightly by nucleus because they are further away
-Also due to more inner electrons, stronger shielding effect (electron repulsions)

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6
Q

What happens to atoms as you cross a period and why?

A

atoms get smaller:

-Bigger nucleus charge (more protons) holds outer electrons tighter
SAME NUMBER OF ELECTRON SHELLS

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7
Q

Working out which radius is bigger: covalent v ionic radius

A

Na 2,8,1 bigger radius
Na+ 2,8 smaller radius

Covalent radius is bigger as it has one more energy level

F 2,7 p=9+ e=9- smaller radius
F- 2,8 p=9+ e=10- bigger radius

Ionic radius is bigger as protons have more electrons to pull (more electrons need to be pulled by the same number of protons)

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8
Q

What is ionisation energy?

A

Energy required to remove one mole of electrons from one mole of atoms in the gaseus state

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9
Q

2nd ionisation energy?

A

energy required to remove one mole if electrons from one mole of 1+ ions in the gaseus state

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10
Q

Na- Why is the 2nd ionisation energy much bigger than the 1st?

A

Because it’s removing an electron from a STABLE OUTER SHELL

More strongly attracted to the nucleus

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11
Q

What happens to the 1st ionisation energy as you descend a group?

A

gets smaller (electrons are easier to move)

Outermost electron is further from the nucleus (larger radius) and not held as tightly

Shielding/screening effect from inner electrons

-more shielded from nuclear pull
-less strongly attracted by nucleus

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12
Q

What happens to the 1st ionisation energy as you cross a period?

A

gets bigger (electrons are more difficult to remove)

Outermost electrons are held more tightly by increasing nuclear charge (more protons)

-less shielded from nuclear pull
-more strongly attracted by nucleus

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13
Q

Is removing an electron endo or exo

A

endo -

energy is needed

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14
Q

What is electronegativity?

A

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

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15
Q

What happens to electronegativity as you go to down a group?

A

Decreases (less pull on bonding electron)

Because the screening effect due to inner shell electrons means there is less attraction between the nucleus and the bonding electrons (atom gets bigger)

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16
Q

What happens to electronegativity as you cross a period?

A

Increases

Covalent radius decreases, nucleus charge increases so greater attraction for bonding electrons

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17
Q

Metallic elements

A

Li Be Na Mg Al K Ca

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18
Q

Monatomic elements

A

He Ne Ar

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19
Q

covalent molecular elements

A

C (half) N O F P S Cl

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20
Q

Covalent network elements

A

B C(half) Si

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21
Q

Metallic bonding: definition and properties

A

Strong electrostatic force of attraction between the - delocalised electrons and the + ions

In general, high mp+bp
(alkali metals are lower)
Conductors of electricity due to delocalised electrons

more outer electrons=more delocalised electrons=stronger metallic bonds=higher mp+bp

22
Q

What are monatomic elements?

A

-exist ad single atoms
-noble gases exist as monatomic elements
-contain no intramolecular forces

23
Q

Intra molecular forces

A

STRONG
hold atoms together in a chemical

24
Q

Intermolecular forces

A

weak
Exist between atoms/compounds (van der waals forces)

25
Q

LDFs

A

London dispersion forces (type if van der walls intermolecular force)

-Forces of attraction that can operate between all atoms and molecules
-Formed as a result if electrostatic attractions between temporary dipoles and induced dipoles caused by the movement/uneven distribution of electrons in atoms and molecules
-The strength of LDFs is related to the number of electrons within an atom or molecule

-weakest of the intermolecular forces
-attraction between temporary dipoles/induced dipoles
-caused by the wobble (imbalance of the position) of electrons

26
Q

Why does the boiling point increase going down the noble gases?

A

Because going down the group the number of electrons in the atom increases so that the size of the dipole increases so greater attraction between atoms

27
Q

List of covalent molecules

A

Diatomic-H2 N2 F2 O2 Cl2
Polyatomic-P4 S8
Fullerenes-C60 (buckyballs)

Mp+bp S8>P4>Cl2
More atoms=more/stronger LDFs=higher mp+bp

28
Q

C60

A

Fullerenes
Buckyballs
Covalent molecules with higher mp+bp due to the large number of atoms—>stringer/more LDFs

29
Q

Examples of Covalent Networks

A

ELEMENTS
B, C(diamond,graphite), Si can be categorised as covent networks

COMPOUNDS
silicon dioxide
silicon carbide

30
Q

Ionic compounds

A

Electrostatic force of attraction between positive and negative ions

Ionic formulae can be written giving the simplest ratio if each type if ion in the substance

Ionic compounds form lattice structures of oppositely charged ions

31
Q

Covalent bonding

A

Atoms share pairs of electrons

The covalent bond is a result of two positive nuclei being held together by their common attraction first the shared pair of electrons

32
Q

What are polar covalent bonds formed?

A

When the attraction if the atoms for the pair of bonding is different (due to different electronegativity values between 2 atoms)

Delta positive and delta negative notation can be used to indicate the partial charges on atoms, which give rise to a dipole

33
Q

Bonding continuum

A

Pure covalent bonding->polar covalent bonding->ionic bonding

34
Q

Ionic character

A

The difference in electronegativities between bonded atoms fives an indicatkon kf the ionic character..

If the difference is large then the movement if bonding electrons from the element of lower electronegativity to the element if higher electronegativity is complete, resulting in the formation of ions

The higher the difference in EN—>the more polar—>the more ionic

35
Q

What happens as you go down the halogen group? (from F to I)

A

Atoms get bigger (more electron shells, more electrons)—>LDFs will be stronger—>mp+bp will increase

36
Q

When is a polar molecule described as polar?

A

When it has a permanent dipole (due to the difference of electronegativity between atoms)

The spatial arrangement (symmetry) of polar covalent bonds can result in a molecule being non-polar

-There must be a difference in electronegativity
-It is not symmetrical

37
Q

Symmetrical atoms and molecules

A

-diatomic elements (non-polar anyways)
-hydrocarbons )alkenes, alkanes, alkynes)
-CO2
-A central carbon attached to the same 4 atoms

DRAW IT FLAST FIRST

38
Q

What is the intermolecular force between molecules with a permanent dipole called?

A

permanent dipole-permanent dipole (polar-polar) attraction/interactions

39
Q

How to test polarity?

A

Polar/non-polar substances in a burette and into a beaker

Charged balloon or rod

Stream of polar substance will bend

40
Q

Hydrogen bonds

A

strongest intermolecular forces

strongest pd-pds due to the higher different in ENs (highly polar)

N, F, O have the highest ENs so form H2 bonds

Weaker than a covalent bond

41
Q

Why are carboxylic acids and alcohols very polar?

A

presence of H bond

42
Q

What is a solvent?

A

A liquid that substances dissolve in?

Can be polar or non-polar

43
Q

What are immiscible liquids?

A

Liquids that don’t mix eg water and oil

44
Q

Are non-polar liquids miscible or immiscible?

A

miscible

45
Q

1-What type of solvent usually dissolves polar molecules?

2-What type of solvent usually dissolves non-polar molecules?

A

1-a polar solvent (eg water which is a polar molecule so a polar solvent)

2-a non/polar solvent

46
Q

What is viscosity?

A

the ‘thickness’ of a liquid

47
Q

What tests can we use to check viscosity?

A

-substance in burette—> the longer it takes to empty, the more viscous

-glass rod with lids on both ends. Turn upside down (air bubble forms)—> the longer it takes the bubble to reach the top, the more viscous

-measuring cylinder and drop ball bearing in—> longer it takes to drop to the bottom, the more viscous

48
Q

What is volatility?

A

How easily something evaporates

49
Q

2 factors that affect volatility

A

strength of intermolecular forces—>the stronger the forces, the less volatile

size of molecule—>the bigger the molecule, the less volatile

50
Q

Why does ice float on water?

A

H bonding between molecules in ice results in an expanded structure that causes the density of ice to be less than that of water at low temperatures.

Chemistry H (11 decks)

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