HL Chem: Unit #2 - Atomic Structure

isoelectronic

any species (atoms and ions) that have the same # of electrons

Effective nuclear charge

the net positive charge that is attracting the electron.

Zeff= atomic # (protons) - total inner electrons

higher nuclear charge

smaller atom

lower nuclear charge

larger atom

shielding effect

the decrease in force of attraction of the nucleus of the valence electrons caused by the presence of electrons in inner energy levels. inner electrons take up more pos. charge and dont let valence electrons/outer electrons feel full pos. charge —> shielding outer electrons

more energy levels equals

bigger atom

positive ion

smaller ion

negative ion

larger ion, adding more electrons increases size due to electron electron repulsion

atomic radius

the distance from the nucleus to the outermost energy level

atomic radius across period

Decreases. zeff increases while there is constant shielding. electrons are drawn closer to the nucleus causing decreased atomic radius

atomic radius down the group

increases. since energy levels are increasing, the attraction between the outer electrons and the nucleus is wekaer. the inner electrons shield the valence electrons so the zeff remains the same. outer electrons are held weakly due to increased energy levels and more space between valence electrons and nucleus causing atomic radius to increase.

ionization energy

the amount of energy to remove the first(farthest) electron from an atom

ionization energy across period

Increases. there is a higher degree of attraction for electrons from the positively charged nucleus going across period. it becomes more difficult to remove an electron from an atom so more energy is needed.

ionization energy down a group

decreases. the number of energy levels increases down a griup and attraction between the outer electrons and the nucleus is weaker so its easier to remove an electron so less energy is required

electron affinity

the energy released when an electron is gained by an atom(non metals). how much it wants electron

more energy give off means (electron affinity)

more stable

electron affinity across period

increases. the attraction for an electron increases due to the increasing zeff therefore more energy is given off when an electron is gained especially for non metals like halogens

electron affinity down the group

decreases. the number of energy levels increases as you go down and outer electrons are weakly attracted to nucleus therefore the attraction for an electron is weaker so less energy is given off

ionization energy: boron and beryllium

Boron: the 2p orbital is further away from the nucleus and is higher in energy and there is a lower attraction of 2p electron by nucleus therefore less energy is required to move 2p electron

Beryllium: held closer to nucleus, higher attraction of electrons for nuclear charge (protons) therefore more energy needed to remove electron so increase ionization energy

ionization energy exception: nitrogen and oxygen

the electrons are facing electron-electron repulsions and there is increased atomic size which reduces the attraction forces between nucleus and electrons, electron electron repulsions mean less energy to remove electron

chemical reactivity

reactivity of a metals depends on how easily it will lose electrons while non metals chemical reactivity depends on electron affinity

highest electronegativity on pt

fluorine - top right corner of pt

lowest electronegativity on pt

francium - lower left corner of pt

protons and neutrons located in

nucleus

radioisotopes

radioactive as nuclei break down releasing high enrrgy particles - harmful to human tissues

isotopes

atoms that contain same # of protons but diff # of neutrons

mass spectrometry

analytical technique that ionizes and then separates atoms/molecules based on their mass to charge ratio (m/z) —> charge usually 1

• allows for the determination of masses of atoms or compounds

• enables for the determination of isotopes for elements, their masses and abundance

vaporization -mp

sample can be anything gaseous

ionization - mp

electron gets knocked out of sample, taking fast moving electrons to shoot at sample but since they are moving very fast, electron gets knocked out

acceleration - mp

every ionized particle should move at same speed and should be subjected to magnetic field

deflection - mp