foundations in chemistry, 2

What is an isotope?

An isotope is an atom with the same number of protons but a different number of neutrons because it has either lost or gained one from another electron. This gives it either a + or - charge

What is Carbon-12?

it is the international standard of measurement of atom masses.

The mass of carbon 12 = exactly 12 atomic mass units (12u). 1 atomic mass = 1/12th of an atom of carbon 12. 1u= mass of a proton or a neutron

What is relative isotopic mass

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

what does atomic mass mean

the number of protons in an atom

what is the realtive atomic mass?

the weighted mean mass of a molecule relative to 1/12th of the mass of carbon-12 atom

what is an acid ?

a proton donor. Releases H+ ions when in an aqueous solution.

what is an alkali

releases OH-

describe the difference between a strong and week acid.

strong acids completely dissociate in aqueous solutions- non reversible reaction

weak acids partially dissociate in aqueous solutions- reversible reaction

what is a base

A proton acceptor. Neutralises an acid to form salts. An alkali is a base dissolved in water to releas OH- ions

What is a redox reaction?

when an oxidation and reduction reaction takes place at the same time. We can use oxidation numbers to identify whats being reduced and oxidised in more complex equations when its not as obvious.

what does the term ionisation energy mean?

the amount of energy required to remove 1 electron from each atom in 1 mole of gaseous atoms of an element to make 1 mole of gaseous 1+ ions

write the first 3 ionisation energy equations of helium

He g → he g+ + e-

he+ g → he 2+g + e-

he 2+ → he 3+g + e-

what happens to the nuclear charge as you go down group 7

nuclaer charge increases but so does sheilding, meaning nuclear attraction decreases, but the atomic radius does increase.

what are shells

regarded as energy levels, energy increases as the number of shells increase. Shells are given as the formula n

shell 1= 2 e-, shell 2= 8e-, shell 3= 18e-, shell 4= 32e-

what are orbitals

regions around the nucleus that can old up to 2 electrons. s,p,d,f orbitals

s-orbital

drawn as a circle, each 1 shell contians one s orbital, the greater the shell number, the greater the radius of the orbital

p orbital

each shell from n=2 contains 3 p-orbitals, the greater the shell number of n the further the p orbital is from the radius

d and f orbitals

d = each shell from n=3 contains 5 d orbitals

f= each shell from n= 4 contains 7 f-orbitals

what is the order of energy of orbitals

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s,

what is an ionic bond

elctrostatic attraction between oppositely charged ions

why does higher sub shells have a smaller first ionising strength

it is easier to remove an electron when there is already more energy present, so less energy is required to remove it. smaller the srength the easier it is to remove

what ions are always soluble

group 1, ammonium, nitrate, hydrogen carbonate,

halides- not though with ag, pb,hg

sulfate- not though with ag,pb,ca,sr,ba

what ions are insoluble

all not with ammonium and group 1

oxide(ca, ba) carbonate, hydroxide (ca,mg,sr,ba) sulfide, dichromate(ca,mg)

defintion of a strong acid

fully dissociates in water ti release H+ ions

definition of weak acid

partially dissociates in water

what does brønsted lowry base mean

a proton acceptor

what doe an alkali mean

a base that is soluble in water and releases OH- ions

what is the defintion of a salt

the ionic compound formed when the H+ ions in an acid are replaced by positive metal ions or ammounium ions

what does ammount of substance mean

the number of things in a set amount of something e.g number of people in a house

what is a mole

the amount of substance containg as many particles as there are carbons atoms in exactly 12g of the carbon 12 atom

definiton of molar mass

the mass per mole of substance

defintion of empirical formula

the smallest whole number ratio of atoms of each element present

defintion of molecular formula

the actual number of atoms present

what does anhydrous mean

an ionic solid that dosent contain any H2O molecules

what does hydrated mean

an ionic solid that does contain H2O molecules/ contains water of crystallisation

What does electronegativity mean

The ability for an atom to attract electrons

Linear shape

2 bonded pairs

0 lone pairs

180

Triganal planar

3 bonded pairs

0 lone pairs

Bond angle of 120

Tetrahedral

4 bonded pairs

0 lone pairs

Bond angle of 109.5

Octahedral

6 bonded pairs

0 lone pairs

Bond angle of 90

Trigonal pyramidal

3 bonded pairs

1 lone pair

Bond angle of 107

Non linear

2 bonded pairs

2 lone pairs

Bond angle of 104.5

What is meant by polar

Uneven share of electrons in a covalent bond due to uneven electronegativites

Identifying polar

Asymmetrical

0>n> 1.8

What causes London forces

Electrons are constantly moving

Distribution could become unsymmetrical, resulting in a temporary dipole

The dipoles induce dipoles in neubghbouting atoms, creating an attraction

What is a permanent dipole dipole bond

Formed by polar molecules

what does water of crystilisation mean

water molecules that form an essencial part in the crystilisation of molecules

why is Oxygen classified as a P-block element

because its highest energy electrons are found in the p orbital

what does atomic number mean

the number of protons in a nucleus

why does aluminum has a lower 1st IE than Mg

Al is in a higher energy subshell which requires less energy to remove an electron

why does oxygen have a lower IE then Ni

in O2 paired electrons repel eachother, meaning less energy is required to remove an electron