topic 1: atomic structure and the periodic table

Isotopes are atoms of the same element with the same number of protons, but different numbers of neutrons

the mass of one atom of an isotope compared to one twelfth of the mass of one atom of carbon-12

the average weighted mass of an atom of an element compared to one twelfth of the mass of one atom of carbon-12

the average mass of a molecule compared to one twelfth of the mass of one atom of carbon-12

R.A.M =  (isotopic mass x % abundance)/100

• have been included in planetary space probes so that elements on other planets can be identified. elements on other planets can have a different composition of isotopes • drug testing in sport to identify chemicals in the blood and to identify breakdown products from drugs in body • quality control in pharmaceutical industry and to identify molecules from sample with potential biological activity • radioactive dating to determine age of fossils or human remains

the energy required when one mole of gaseous atoms forms one mole of gaseous ions with a single positive charge. H(g) –> H+ (g) + e-

the energy required when one mole of gaseous ions with a single positive charge forms one mole of gaseous ions with a double positive charge. Ti+(g) —> Ti2+(g) + e-

1.the attraction of the nucleus (the more protons in the nucleus the greater the attraction) 2. the distance of the electrons from the nucleus (the bigger the atom the further the outer electrons are from the nucleus and the weaker the attraction to the nucleus) 3. shielding of the attraction of the nucleus (an electron in an outer shell is repelled by electrons in complete inner shells, weakening the attraction of the nucleus)

its first electron is in the first shell closest to the nucleus and has no shielding effects from inner shells. He has a bigger first ionisationenergy than H as it has one more proton

as one goes down a group, the outer electrons are found in shells further from the nucleus and are more shielded so the attraction of the nucleus becomes smaller

as one goes across a period , the number of protons increases making the effective attraction of the nucleus greater. the electrons are being added to the same shell which has the same shielding effect and the electrons are pulled in closer to the nucleus

this is because Na will have its outer electron in a 3s shell further from the nucleus and is more shielded. so Na’s outer electron is easier to remove and has a lower ionisation energy

Al is starting to fill a 3p sub shell, whereas Mg has its outer electrons in the 3s sub shell. the electrons in the 3p subshell are slightly easier to remove because the 3p electrons are higher in energy and are also slightly shielded by the 3s electrons

with sulphur there are 4 electrons in the 3p sub shell and the 4th is starting to doubly fill the first 3p orbital. when the second electron is added to a 3p orbital there is a slight repulsion between the two negatively charged electrons which makes the second electron easier to remove

An atom fills up the sub shells in order of increasing energy (note 3d is higher in energy than 4s and so gets filled after the 4s 1s2s2p3s3p 4s3d4p5s4d5p

spherical

dumbbells

2 arrows going in the opposite directions in a box

s - 2 electrons p - 6 electrons d - 10 electrons f - 14 electrons

the repeating pattern of physical or chemical properties going across the periods

decreases ,because the increased number of protons create more positive charge attraction for electrons which are in the same shell with similar shielding

increases due to increasing number of protons as the electrons are being added to the same shell

there is a small drop between Mg + Al. Mg has its outer electrons in the 3s sub shell, whereas Al is starting to fill the 3p subshell. Al’s electron is slightly easier to remove because the 3p electrons are higher in energy