Atomic Struc

Atom is the smallest particle found in an element that can take part in a chemical rctn

E- in orbitals around nucleus, 1/1840 , -1, (0 -1) e Neutron - nucleus, 1, 0, (1 0) n Proton -nuclues, 1, +1, (1 1) p

• Same speed • diff direction of deflection • diff angle of deflection

angle of deflection prop. to | q/m | when solving qn use the constant k

any species of given mass no. and atomic no. (eg hydrogen - 1) - elemental name & mass no

mass no

nucleon no.

proton no.

determines the identity of an atom

same no. of protons/e- but diff neutrons - same chem properties n diff/masses/phy properties

Nucleon no. of Y = 235+1-90-2 = 144 Proton no. of Y = 92-36 = 56 Hence Y = (144 56) Ba

Subshells: s, p, d, f S: 1 - spherical shape, non directional P: 3 -dumbbell shape, directional as the e- density is concentrated in certain directed along…axes D: 5 - d xz & d xy & d yz - 3 orbitals with similar 4-loped shape, orbitals have their lobes pointing b/w the axes d x^2 - y^2 - 4 lobed shape, lobes aligned along the x & y axes d z^2 - dumbbell shaped surrounded by a small doughnut shaped ring at its waist, orbital is aligned along the z axis

further the shell is from the nucleus, higher the energy lvl of the shell higher the energy lvl of the shell/e- weaker the electrostatic attraction b/w nuceus and e- larger size of orbital

4s<3d

Aufbau principle - e- fill orbitals from the lowest energy orbital upwards Hund’s rule - orbitals of a subshell must be occupied singly by an e- of parallel spins before pairing can occur Pauli exclusion principle - each orbital can hold a max of 2 e- and they must be of opp. spins

when they spin in opp directions, the magnetic attraction which results from their opp spins can counterbalance the electrical repulsion which results from their identical charges

Cr & Cu - a ‘d’ subshell that is half-fulled or full is more stable - for Cr: as 3d & 4s are abt equal in energy by the time Cr is reached, so by having 1 e- each in the 4d and 4s orbitals, inter-electronic repulsion is minimized For Cu: the fully filled 3d subshell is unusually stable due to the symmetrical charge distribution around the metal center

one or more e- absorb energy and are promoted to a higher energy lvl

once e- occupy the inner 3d orbitals, they provide some shielding for the outermost 4s e- hence they repel the 4s e- to a slightly higher energy lvl

species with the same total no. of e-

s- block - ns^1 ns&2 d-block - (n-1)d1 ns^y - the 1 is starting from the first transition metal p-block - ns^2np^1 -> ns^2np^6

Half the shortest inter-nuclear dist found in the struc of the element

DECREASE as No.of e- shells remain the same no. of protons, hence nuclear charge increases e- increase but since they are added to the valence shell, the shielding effect remains approx const effective nuclear charge increases electrostatic attraction b/w nucleus and valence e- increases decrease in size of e- cloud

INCREASE although protons increase, nuclear charge increases no. of e- shell increases, dist b/w nucleus and valence e- increase hence, the electrostatic attraction b/w the nucleus and the valence e- decreased increase in size of e- cloud