Topic 3: Periodicity

given by the atomic number and increases between succesive elements as protons are added to the nucleus/ - ability of an atom to attract increases with group number but remain the same down a group

the energy change when 1 mole of electrons is added to one mole of gaseous atoms X(g) + e- —> X-(g)

energy require to remove one mole of electrons from one mole of gaseous atoms in their ground state • measure of attraction between nucleus and outer electrons

ability of an atom/nucleus to attract electrons in a covalent bond/molecule. • It is an artificial scale from 0.7 to 4.0, created by combining the ionisation energy and the electron affinity of the elements.

bases soluble in water which from a basic solution (hydroxide ions)

(down) elements with the same number of valence electrons

(across) The period number (n) is the outer energy level that is occupied by electrons.

half the distance between the nucleus’s of 2 bonded atoms of the same element -atomic radii decrease along a period as the nuclear charge increases and electrons are added to the same outer shell. The attraction between the outer electrons and nucleus increases.

: Cations are smaller than their parent atoms, as the formation of positive ions involves the loss of the outer shell.

S; Alkali Metals; reactive metals

P; Halogens; reactive group of non-metals

S; alkaline earth metals

P; Noble gases; stable non metals

D; transition metals

The transition metals are in the large section of d-block elements in the middle of the Periodic Table from Sc to Zn, etc. Zn is not a transition metal because it does not form ions with incomplete d sub-levels.

• has physical and chemical features of non metals and metals are are in the P block of the periodic table along the staircase

reduces the attraction of nucleus to the outer electrons

one proton is added to nucleus; one electron added to calance energy shell= effective nuclear charge increases with nuclear charge as there is no change in number of inner electrons

• increase in nuclear charge= increase in number of inner electrons • remains more or less the same down a group

• positive ions are smaller than parent ions (Na+ smaller than Na) • negative ions larger than parent ions (Cl- larger than Cl) • ionic radii decrease from Groups 1-14 fo rpositive ions (increased attraction between nucelus and electrons pulls outer shell closer to nucleus) • ionic radii decrease down Group 14-17 for negative ions (decrease in ionic radii due to icnrease in nuclear charge across period) • ionic radii decrease down a group as number of electron energy level increases

• ionization energies increase across a period (due to increase in effective nuclear charge that causes an increase in attraction between outer electrons and nucleus; makes electrons harder to remove) • ionizzation energies decrease down a group (electron removed is from the energy level furtherest form nucleus; effective nuclear charge about the same; increased distance between electrons and nucleus reduces attraction between them)

• g17 elements have incomplete outer energy levels; high effective nuclear charge; attract electrons the most • g1 metals have low effective nuclear charge + attract electrons the least

• increases across period due to increase in nuclear charge (increase attraction between nucleus and bond electrons) • decreases down a group (bonding electrons are furthest from nucleus; reduced attraction)

• melting point decreases down group (attractions decrease with distance due to delocalized outer electron and positive ion attractive forces) • reactivity increases down group (francium highest)