Chemistry EOT atomic structure

atom defenition and subatomic particle defenition

atom - smallest part of an element that can exist

subatomic particle - smaller fundamental components that make up atoms

Greeks and Dalton's Atomic Theory

tiny solid spheres that were small indivisible particles

Ex - more favourble way to say when you discover

you give evidence to prove the existence of

JJ Thompson - electron discovery - plum pudding model

in 1897 scientists (JJ Thompson) discovered that atoms contain tiny negatively charges particles - electrons

this then showed that atoms must have an internal structure and werent tiny indivisible spheres

thompson proposed the plum pudding model which was that an atom was a solid sphere of positive charge with negatively charged electrons embedded in it

alpha scattering experiment - this was to see if the plum pudding model was right

took a piece of gold foil (gold because it can be hammered into very thin foil, just a few atoms thick)

then fired tiny + ⍺ particles (He2+) at the foil.

most of the particles went straight through the foil without

changing direction, sometimes particles were deflected repelled, (change direction)

and then some bounced back (reflection)

importance of the alpha scattering experiment

and importance of using and developing models

radically changed the way we think about atoms

New experimental evidence may lead to a scientific model being changed or replaced.

why the new evidence from the scattering experiment led to a

change in the atomic model

The fact that most of the ⍺ particles went straight through the foil showed that atoms were just empty space (so plum pudding model was wrong)

the fact that some ⍺ particles were deflected (repelled) showed that the centre of the atom must have a positive charge as + charge is needed to repel + charged ⍺ particle

the fact that some ⍺ particles bounced straight back showed that the centre of the atom, called the nucleus must contain a great deal of mass

differences between plum pudding model and nuclear model (V1) - nucleus and mass USE NEEM abbreviation

the pp model is a sphere of positive charge with negatively charged embedded electrons but in the nuclear model (all) the positive charge is held in (by) the nucleus

The mass in the plum pudding model is spread out through the sphere. (most of) the mass in the nuclear model is concentrated in the nucleus.

differences between plum pudding model and nuclear model (V1) - electrons empty space and modern model

in the plum pudding model, electrons are embedded but in the nuclear model the electrons and nucleus are separate (electrons are in orbits)

because the electrons in nuclear model are in orbits around the nucleus in the nuclear model, most of the atom is empty space but the pp model has no empty space and is solid

nuclear model (modern) contains protons and neutrons whereas pp doesnt

describe the nuclear model V1

most of the atom is empty space in the centre there is the positive dense nucleus which contains most of the mass of the atom around the nucleus there are tinier negative electrons in orbits,

further discoveries modified nuclear model v1 to modern nuclear model

Niels Bohr proposed that electrons orbit the nucleus at specific distances rather than a general which we know as shells or energy levels (based on calculations he had carried out) - accepted as agreed with results of other scientists

several yrs later scientists found out that the positive charge (chadwick) in the nucleus is due to tiny positive particles - protons - number of protons determines amount of positive charge in the nucleus

about 20 yrs after the nuclear model was proposed, Chadwick discovered neutrons in the nucleus - the neutral charge was late to be discovered as it wouldnt attract or repel any charges

describe (modern) + final nuclear model

most of the atom is empty space in the centre there is the positive nucleus which contains most of the mass (containing protons and neutrons) outside the nucleus electrons orbit at specific energy levels .

order of stuff discovery

1. atom 2. electron 3. (+) nucleus 4. electron energy levels

5. proton 6. neutron

relative charges and masses of subatomic particles

proton - relative charge : 1 relative mass : 1 , found in nucleus centre of atom

neutron - relative charge : 0 relative mass : 1 , found in nucleus centre of atom

electron - relative charge : -1 relative mass : very small , found in electron shells / energy levels nucleus orbital

the overall charge of the nucleus Is ___________ ?

the overall charge of an atom is _____________ ?

nucleus positive as protons (1) + neutrons (0) = positive (1)

atoms is neutral as there must always be same number of protons to electrons for the atom to be stable (stable atoms are neutral) and neutrons are side pieces as they dont have any charge

to find how many of what subatomic particle is in periodic table by symbols

electron and proton : number on atomic proton number

neutrons : mass number - atomic proton number

mass no.

number of protons , neutrons and electrons

mass number is up and atomic proton number is down - mass number is always bigger

The mass of electrons are neglected because their relative mass is very small, (but you can work it out as protons = electrons)

isotopes

atoms of an element with the same number of protons (therefore) electrons with a different number of neutrons resulting in a different mass no.

Relative atomic mass (Ar)

the average mass number of an element from their isotopes weighted by the abundance of each isotope relative to 1/12 of Carbon 12

- higher abundance make the Ar closer to that mass number - periodic tables often round this

ion

atoms or groups of atoms which have an overall electrical charge charge because they have lost or gained electrons in their outer shell

(electrons are -) so positive ions have lost electrons whereas negative ions have gained electrons

Ar formula

Ar =

Sum of (isotope abundance (%) x isotope mass number)

÷

100

electron config facts

electrons occupy energy levels and the one closest to the nucleus is the lowest energy level - only certain number of electrons are allowed in each shell.

shell 1 . 2 elec. shell 2. 8 elec. shell 3. 8 elec. (max)

it can be written as formula as shell[1,2,3,4] e.g. calcium [2,8,8,2]

draw them with crosses and ofen exist in pairs

octet rule

the fact that noble gases are unreactive because they have full outer shells shows that in other elements their outer shell is not full which make them want to react to achieve a full outer shell.

ionic bonding - how ion charge links to group

reacting that takes place losing or gaining electrons forming ions and being attracted by strong electrostatic forces - between non metal and metals

because ions react to achieve a full outer shell so the number tells how many outer electrons need to be lost or gained to achienve a full outer shell

ion charge to group no

group : 1 2 3 4 5 6 7 0

ion charge : 1+ 2+ 3+ no ion. 3- 2- 1- no ion

metals form + ions (cations)

non metals form - ions (anions)

When naming ions u assume they are reacted so u always use IDE

ammonium sulfate nitrate carbonate hydroxide bicarbonate phosphate cyanide molecular ions

ammonium - NH4(+) Bicarbonate - HCO3(-)

sulfate - SO4(2-) phosphate - PO4(3-)

Nitrate - NO3(-) cyanide - CN(-)

carbonate - CO3(2-)

mendeleev

he developed his perioidic table in order of increasing atomic weight and not proton no. because protons were not discovered until the early 1917 and mendeleev developed in 1869

he often left gaps and changed the order in which elements were placed to make sure that the elements were placed in a group of similiar properties

Reactivity - tendency to form ions

We can see in the periodic table that other elements are more reactive than others, because they form ions easier, e.g. group 1 is easier because it only needs to lose 1 electron

and group 7 is also easier because it also only needs to gain 1 electron

compared to other groups