Topic 3 + 13 Flashcards
1
Q
lanthanoids
A
- 1st row of f-block
- metal
2
Q
actinoids
A
- 2nd row of f-block
- metal
3
Q
metalloids
A
- have characteristics of both metals & non-metals
- similar physical properties & appearance to metals
- similar chemical properties to non-metals
- B, Si, Ge, As, Sb, Te, Po
4
Q
liquid at SATP (298K, 100kPa)
A
- Br (Bromine), Hg (Mercury)
5
Q
gas at SATP (298K, 100kPa)
A
- H, He, N, O, F, Cl, He, NE, Ar, Kr, Xe, Rn
6
Q
effective nuclear charge (Zeff)
A
- attractive positive charge of nuclear protons acting on valence electrons
- Zeff experienced by outer e- < full nuclear charge
- Zeff = (# of total e-) - (# of inner e-)
- increases left to right, bottom to top
7
Q
atomic radius
A
- not intuitive
- increases down a group bc # of occupied electron shells increase
- decreases across a period bc attraction btwn nucleus & electrons increases as nuclear charge increases
8
Q
ionic radius
A
- positive ions have smaller ionic radius than parent atoms due to loss of outer shell
- negative ions have bigger ionic r than parent atoms due to increased electron repulsion in outer principal E level
- decreases from groups 1-14 for positive ions due to increase in nuclear charge (increased attraction btwn nucleus & electrons pulls outer shell closer to nucleus)
- decreases from group 14-17 for negative ions due to increase in nuclear charge
- increases down a group as # of electron energy levels increase
9
Q
first ionization energy (I1)
A
- energy required to remove 1 mole of electrons from ground state of 1 mole of gaseous atom
- [ H(g) -> H+(g) + e- ]
- always endothermic & positive value
- measure of attraction btwn nucleus & outer electrons
- increases across a period bc increase In Zeff causes increase in attraction btwn outer electrons & nucleus, making electrons harder to remove
- decreases down a group bc increased distance btwn electron and nucleus due to # of electron energy levels increasing reduces attraction btwn e- and nucleus
- opposite trend of atomic radii
10
Q
small departures from first ionization trend
A
- provide evidence for division of energy levels into sub-levels
- group 2 [ns2] has greater I1 than group 13 [ns2p1]: p orbitals have higher energy than s orbitals
- group 15 [ns2npx1py1pz1] has greater I1 than group 16 [ns2npx2py1pz1]: electron removed from group 16 is taken from doubly occupied p-orbital (unlike group 15). It is easier to remove as it’s repelled by its partner
11
Q
first electron affinity
A
- change in energy when 1 mole of electrons is added to 1 mole of gaseous atoms to form 1 mole of gaseous ions
- [ X(g) + e- -> X-(g) ]
- exothermic & negative
- negative of I1 of anion
- group 17: attract e- the most bc incomplete outer E level & high Zeff (≈+7)
- group 1: attract e- the least bc lowest Zeff (≈+1)
- group 2&15: maximum EA bc
- group 2 [ns2]: added e- must be placed into p-orbital which is further from nucleus and experiences reduced electrostatic attraction due to shielding from electrons in s-orbital
- group 15 [ns2npx1py1pz1]: added electron must occupy p-orbital that’s already singly occupied. so attraction btwn electron & atom is less than expected due to increased electron repulsion
12
Q
electron affinity
A
- not available for noble gases as they generally don’t form negatively charged ios
- 2nd & 3rd EA: endothermic & positive bc added e- is repelled by the negative charge
- e.g. 2nd EA for oxygen [ O-(g) + e- -> O2-(g) ]
13
Q
electronegativity
A
- measure of ability of its atom to attract electrons in covalent bond
- measure of attraction btwn nucleus and outer electrons that are bonding
- element with higher EN have higher electron pulling power
- element with lower EN have lower electron pulling power
- increases left to right across period bc increase in Zeff leads to increase in attraction btwn nucleus & bond electrons
- decreases down a group bc bonding electrons are further from nucleus and more shielded, reducing attraction
- doesn’t apply to group 18 bc they don’t form covalent bonds
14
Q
compare/contrast electronegativity and ionization energy
A
- same general trend as ionization energy
- ionization energy is directly measured and property of gaseous atoms (only)
15
Q
compare/contrast electronegativity and electron affinity
A
- elements with higher EN have most exothermic EA
- EA: property of isolated gaseous atoms
- EN: property of atom in molecule
16
Q
metals vs. non-metals
A
- non-metals have higher ionization energy & electronegativity
- metals can conduct electricity bc their valence electrons can move away from nucleus. valence electrons form a sea of electrons around fixed metal cations
17
Q
melting point
A
- very complex since it depends on bonding & structure of elements
- simple for group 1 & 17
- group 1: melting point decreases down the group bc its metallic structure is held together by attractive forces btwn delocalized outer electrons & positively charged ions and this attraction decreases with distance
- group 17: melting point increases down the group bc its molecular structure is held together by weak intermolecular forces (London dispersion forces) and this attraction increases with number of electrons in molecule
- generally rises across a period, max at group 14, fall back to reach minimum at group 18
18
Q
group 3 element that is not solid at room temperature
A
chlorine and argon
19
Q
chemical properties
A
- detemrined by electron configuration of its atoms
- elements of same group have similar chemical properties as they have same number of valence electrons
- group 18: colorless gas, monoatomic, very unreactive bc of inability to lose/gain electrons
- don’t form cations bc highest IE
- don’t form anions as extra e- would need to be added to an empty outer energy level shell where e- would experience negligible Zeff
- stable octet except Helium
- all other atoms: reactive bc unstable incomplete electron energy levels. lose/gain electrons to achieve electron configuration of nearest noble gas
- group 1, 2, 13: lose electrons, generally metals
- group 15, 16, 17: gain electrons, generally non-metals
- metalloids: intermediate properties