Chem exam 2

Electronegativity

-the tendency for an atom to draw electrons toward itself in a chemical bond

-increases across and decreasesdown

monatomic ion

ions formed from only 1 atom

polyatomic ion

electrically charged molecules

oxyanions

polyatomic ions that contain one or more oxygen atoms

Naming polyatomic ions

-ate: more oxygen atoms

-ite: less oxygen atoms

Per- : more oxygen

Hypo: less oxygen

ionic bond

electrons are transferred and ions form

delta en>2

-composed of ions (salts)

-electrostatic forces of attraction between oppositely charged cations and anions

covalent bond

electrons are shared and molecules form

-attractive forces between positive nuclei and pair of electrons between atoms

nonpolar-electrons shared qually (delta en<.5)

-polar- electrons shared unequally (delta en between .5 and 2)

-attraction of each shared electron to both nuclei stabilizes

ionic compounds

metal (atoms readily lose electrons) and nonmetal (atoms gain electrons) transfer of electrons occur and ions formed

-stabilized by electrostatic attractions (ionic bonds) between ions of opposite charge

-solids that melt at high temperatures and boil at even higher temperatures

-electrically neutral

-polyatomic ions can be both cation and anion

-cannot be properly symbolized by molecular formula, need relative numbers of constituent ions

-dissolve easily

molecular compounds

-discrete, neutral molecues

-atoms share electrons

-gases, low-boiling liquids and low-melting solids

-combination of non metals

alkalai metals

-soft

-metallic properties (high electrical and thermal conductivity)

-as you move down, mass density and atomic radii increase while melting point and ionization energies decrease

-1 valence electron, readily lose electron to become cation with noble gas configuration

-excellent reducing agents

-react with nonmetals to form salts

-react with water to form hydrogen gas and solution of alkalai metal hydroxide

-react with hydrogen to form alkali metal hydride

-oxidize easily, stored in mineral atoms

-energy emitted as radiation with characteristic colors

Halogens

nonmetallic group 17

-diatomic molecules

-as move down, mpt + bpt increase

-7 valence electrons, highly reactive

-oxidizing agents

-negative electron affinity

-react with metals to form metal halides (dissolve in water, hyrdrohalic acid)

-react with water to form hydrogen flourine (strong acid) + oxygen (exothermic)

-interhalogen compounds (react with each other)

Noble gasses

-monatomic, gas at room temperature

-high first ionization energy

-stable electron configuration, resist electron addition

-chemical inertness

metallic bond

electron sea, delocalized electrons

chemical bonds

electrons attracted to nucleus of another atom

when lead to net reduction of potential energy, chemical bond formed

-atom with lower EN loses electron and becomes cation

ionic radius

cation-smaller if loses electrons bc strong nuclear pull

anion-larger than its parent atom if it gains electrons, more repulsion

dipole arrow

points towards the negtive effective nuclear charge atom

Naming binary ionic compound

name of metal cation + parenthesized roman-numeral indicating metal charge , anion base name + ide

Naming polyatomic ionic compound

name of metal cation and polyatomic anion name (or oxyanion name)

Naming hydrated ionic compound/ hydrates

name of ionic part + number of water molecules using greek numeral prefix -hydrate

1. mono

2. di

3. tri

4. tetra

5. penta

6. hexa

7. hepta 

8. octa

9. nona

10. deca

Binary molecular compound

1. more metal-like element

2. more nonmettallic element

greek prefix (number of atoms of first element) + first element name then greek prefix + second element -ide

acids

hydrogen containing molecular compounds which dissociat into h ions and water

hydrogen followed by non metal elements

binary acid- hydrogen and nonmetal (hydro + nonmetal base name + ic)

oxyacid- hydrogen and oxyacid anion (ate: base name + -ic, ite: base name +-ous)

molecular formula

shows true composition of a molecule, actual number of atoms

empirical formula

simplest whole number ratio of atoms

Calculating percent composition

1. find molar mass of all elements in compound

2. find molecular mass

3. divide molecular mass by found mass and multiply by 100

Determining molecular formula

1. find molar mass of empirical formula

2. divide molar mass of molecule by empirical formula to find n

3. multiply subscripts by n

cis isomer

same side

trans isomer

anti side

enantiomers

isomers that are mirror images of each other but do not super impose

expanded octet

groups 13-17, exceed by 10 because of full d subshells, charge of cation=group number-10

inert pair effect

relatively low energy of the valence s electron pair for atoms of the heavy elements of groups 13, 14, 15 (Tl+, Sn2+, Pb2+, Bi3+) (Hg-Hg2+) and Hg2+

Transition and inner transition metal elements cations

2+ or 3+, lose s electrons first, sometimes loses one or two d electrons

bond length

distance at which lowest potentail energy is achieved

pure covalent bond

electrons in a bond shared equally, atoms are identical

polar covalent bond

more electronegative atom has greater electron density, partial positive charge on one atom and partial negative charge on the other

binary acids

1. hydrogen is changed to hydro

2. other nonmetallic name adds suffix -ic

3. add the word acid

oxyacids

1. Omit “hydrogen” 2. Start with the root name of the anion 3. Replace –ate with –ic, or –ite with –ous 4. Add “acid”

Coulomb’s law

lattice energy (delta H= product of ion charges/ distance between atoms

hess’s law

total enthalpy change is a sum of all enthalpy change steps

drawing lewis structures for molecular compounds

1. calculate number of valence electrons

2. draw skeletal structure (first atom/ least electronegative listed first)

3. place electron pair between every atom

4. fill rest of electron with lone pairs

odd electron species

odd number of valence electrons and cannot pair

incomplete octet

ex. hydrogen, helium, and lithium form duet

group 2 + 13 form with 4 and 6 electrons

expanded octet

more than 8 valence electrons bc d orbital

formal charge

# of valence electrons - bonds - lone electrons