Atomic Structure All subtopics

proton has charge +1 and relative mass 1; neutron has charge 0 and relative mass 1; electron has charge −1 and relative mass / negligible

protons = 16; neutrons = 32 − 16 = 16; electrons = 16 + 2 = 18

protons deflected towards the negative plate; electrons deflected towards the positive plate by a much larger angle; neutrons not deflected; magnitude of deflection depends on charge-to-mass ratio / electrons have far higher charge-to-mass ratio than protons / neutrons have no charge so experience no force

both elements are in Period 3 / outer electrons in same shell; sulfur has more protons / greater nuclear charge; shielding is approximately the same across the period; outer electrons in sulfur pulled more strongly towards the nucleus / smaller radius

across Period 3 atomic radius decreases; nuclear charge increases by one proton per element; electrons added to the same outer (third) shell; shielding by inner shells remains approximately constant; effective nuclear attraction on outer electrons increases; outer electrons pulled closer to the nucleus; down Group 2 atomic radius increases; each successive element has one additional occupied electron shell; outer electrons are further from the nucleus; inner shells provide greater shielding; net attraction on outer electrons decreases despite higher nuclear charge

atoms of the same element / same proton number; with different numbers of neutrons / different mass numbers / different nucleon numbers;

protons = 17; neutrons = 20 (from 37 − 17); electrons = 17;

chemical property — identical / both react the same way (e.g. both form NaCl with sodium); because they have the same number of electrons / same electron configuration; physical property — ³⁷₁₇Cl has greater mass / greater density than ³⁵₁₇Cl because it contains 2 more neutrons;

isotopes have the same number of protons / same proton number; therefore the same number of electrons in a neutral atom; therefore the same electron configuration; chemical reactions depend on electrons / electron arrangement, so chemical properties are identical; isotopes have different numbers of neutrons; this gives them different masses / different mass numbers; greater neutron number gives greater mass and greater density (since atomic volume is essentially unchanged);

6 electrons; because a p sub-shell contains 3 orbitals and each orbital holds a maximum of 2 electrons

Cr: 1s²2s²2p⁶3s²3p⁶3d⁵4s¹; Cr³⁺: 1s²2s²2p⁶3s²3p⁶3d³; (4s electron removed first, then two 3d electrons)

A region of space around the nucleus where there is a high probability of finding an electron; one orbital holds a maximum of 2 electrons

The 4s sub-shell is at a lower energy than 3d in the neutral atom; electrons fill the lowest available energy sub-shell first to give the most stable ground state

Electrons fill the lowest-energy sub-shells first to give the lowest-energy/ground-state configuration; this is why 1s fills before 2s and 2s fills before 2p; within a sub-shell containing several orbitals (such as 2p), electrons occupy separate orbitals singly before pairing/Hund's rule; this minimises inter-electron repulsion because two electrons in one orbital repel more strongly than two in separate orbitals; nitrogen has the configuration 1s²2s²2p³ with three singly occupied 2p orbitals (parallel spins); oxygen has the configuration 1s²2s²2p⁴, where one 2p orbital must contain a pair of electrons while the other two remain singly occupied

Energy required to remove one electron / one mole of electrons; from each atom in one mole of gaseous atoms; to form one mole of gaseous +1 ions

Ca⁺(g) → Ca²⁺(g) + e⁻; correct state symbols (g) on both species

Outer electron in Al is in a 3p orbital / Mg's outer electron is in 3s; 3p is higher in energy / further from nucleus than 3s; 3p electron in Al is shielded by the filled 3s sub-shell, so less energy is needed to remove it

In P, each 3p orbital contains one electron / 3p electrons are unpaired; in S, two electrons must pair in one 3p orbital; spin-pair repulsion between paired electrons makes one electron easier to remove

Large jump occurs between IE₂ and IE₃; two electrons are removed before the jump; outer shell contains two electrons, so Y is in Group 2; Period 3 Group 2 element is magnesium / Mg; the third electron is removed from an inner shell (2p) which is closer to the nucleus / less shielded; this requires much more energy, producing the large jump

Atomic radius increases down the group; shielding by inner shells increases; attraction between nucleus and outer electron decreases / outweighs the increase in nuclear charge