OCR A A level foundations in chemistry flashcards

ionic bond definition

the strong electrostatic attraction between two or more oppositely charged ions

covalent bond definition

the elctrostatic attraction between between the bonding pair of electrons and their nuclei

what’s the maximum number of bonding pairs?

equivalent to the number of electrons in the outer shell.

valence

the measure of many electrons an atom can fit on its outer shell

dative bond

a covalent bond in which both electrons come from the same atom

MOLECULE- 2BP 0LP

linear, 180°

MOLECULE-3BP 0LP

trigonal planar, 120°

MOLECULE-4BP 0LP

tetrahedral, 109.5°

MOLECULE-6BP 0LP

octahedral, 90°

MOLECULE- 5BP 0LP

trigonal bipyramical, 90°, 120°

MOLECULE-3BP 1LP

trigonal pyramidal, 107°

MOLECULE- 2BP 2LP

non-linear/bent, 104.5°

order of repulsion of electrons most to least

lp/lp, lp/bp, bp/bp

electronegativity definition

the ability of an atom to attract the bonding electrons in a covalent bond

what increases electronegativity and why?

in a lower period because there’s less space therefore more attraction between the outer shell and the nucleus, higher group because it has more protons/positive charge to attract the electron pair

dipole definition

the separation of opposite partial charges in a molecule, represented by ẟ+/ẟ-

what determines whether a bond is ionic or covalent?

the difference in electronegativity. covalent is lower, then froms a dipole, then at a high enough difference it forms an ionic bond

average bond enthalpy definition

the amount of energy required to break one mole of bonds of a particular type between two atoms in a gaseous state, caulculated using a variety of different compounds

induced dipole-dipole interactions (london dispersion forces)

the weakest intermolecular force that exists between all molecules due to electron movement

simple molecular lattice

the structure simple covalent molecules form in the solid state. held in place by london forces

solubility of non-polar simple covalent compounds

soluble in non-polar solvents but not in polar solvents

solubility of polar simple covalent compounds

may dissolve in polar substances. doesn’t dissolve in non-polar substances.

conductivity of simple molecular structures

aren’t electrical conductors because there are no mobile charged particles. however some polar structures can ionise

hydrogen bond

a type of permanent dipole-dipole interaction found between H and O,N or F. strongest IM force

anomalous properties of water

solid less dense than liquid. high melting/boiling point. high surface tension

permanent dipole-dipole interactions

the intermolecular force between polar molecules because of their dipoles.

ionic lattice structure

ions arranged in a repeating pattern

solubility of giant covalent structures

generally don’t dissolve because the energy needed to overcome the covalent bonds is too great

conductivity of giant covalent strucutres

sometimes can conduct due to delocalised electrons

what is n=1 n=2 n=3

shell1 shell2 shell3

sub shells

the sum of the one or more orbitals making up the shell of an atom

how many sub shells does each shell have

n=1 has s, n=2 has s + p, n=3 has s + p + d etc

orbital definition

a region of space around the nucleus where an electron is likely to be found. can hold 2 electrons

s orbital shape

spherical

p orbital shape

dumbbell shape

what is in electron configuration

principal quantum no., sub shell, electron occupancy in sub shell

metallic bonding definition

the electrostatic attraction between positive metal ions and negative delocalised electrons

isotope definition

atoms of the same element with a different number of neutrons

relative isotopic mass definition

mass of an isotope relative to 1/12 of a carbon-12 atom

relative atomic mass

the average mass of an atom of an element, considering the isotopic abundances, relative to 1/12 a carbon 12 atom.

empirical formula

the simplest whole number ratio of atoms of each element present in a compound

anhydrous definition

a substance containing no water

hydrated definition

compounds containing water molecules

water of crystallisation meaning

water that is found in the crystalline framework of a metal or salt, but not directly bonded.

how many electrons can fill the first four shells?

2, 8, 18, 32 2n²

hydrochloric acid formula

HCl

sulphuric acid formula

H2SO4

nitric acid formula

HNO3

ethanoic acid formula

CH3COOH

sodium hydroxide formula

NaOH

potassium hydroxide formula

KOH

what is an acid

a proton donor aqueous solution

what is a base

a substance that reacts with an acid to form salt and water/ proton accepting species

what is an alkalai

any base that is soluble in water

what makes an acid strong/weak

how much the acid dissociates in water, releasing H+ ions. if all of its Hs become H+ ions it is strong and fully dissociated, if only some dissociate it is weak and partially dissociated.

what is neutralisation

the exothermic reactions between H+ and OH- to from water. also the reaction between acids and bases to form salts.

general oxidation no. of O

-2

general oxidation number of H

+1

oxidation no. of O in peroxide

-1

oxidation no. of H in metal hydrides

-1

oxidation no. for group 7(halides)

-1 usually but can be -1 to +7

oxidation group 6

-2 usually but can be -2 to +6

oxidation group 5

-3 usually but can be -3 to +5

oxidation no. group 2

+2

oxidation no. group 1

+1

oxidation no. fluorine

-1 always

chlorine oxidation no.

-1 except in compounds with O or F

O oxidation no. in F2O

+2

oxidation no. transition metals

whatever ionic charge it has, e.g Iron(II) is +2, or whatever is left

oxidation no. in group 4

whatevers left/+4

oxidation no. of elements in their natural forms

0

oxidation no. of ions

whatever the charge is (e.g Cl- is -1, Ca2+ is +2)

acid dissociation constant (Ka) meaning

a measure of the strength of an acid in solution. It represents the concentration of hydrogen ions (H+) in solution produced by an acid.

acid dissocation constant formula

amount of substance definition

the measure of how many sets of 6.02×10²³, measured in mol

percentage yield

Percentage of product obtained compared to the maximum possible mass

Avogadro's constant

6.022×10²³

molar mass meaning

the mass in g of one mole of a particular substance

volume of 1 mol of any given gas at room temp and pressure

24dm³

molecular formula meaning

the number of atoms of each element in a compound

ideal gas equation

pV=nRT

(presure*volume=number of moles*gas constant*temperature)

Pa, m³, mol, 8.314, K

Atom economy

the percentage of desired product formed in a reaction over total products formed

why is it good to keep atom economy high?

environmentally sustainable, less waste product formed, less natural resources used

Oxidation definition

The loss of electrons or an increase in oxidation number

Reduction definition

The gain of electrons or the decrease in oxidation number