Chem Exam 2

cations

formed from METALS because they have lower ionization energies than nonmetals thus like to LOSE electrons (lower i.e makes it easier to remove electrons)

• always has positive net charge

anions

formed from NONMETALS b/c they have higher ionization energies and thus like to gain/accept electrons

• always has negative net charge

(high i.e meaning the proton nucleus has a stronger attraction for electrons when we go from left to right across the periodic table)

ionic compound

formed when a metal LOSES its valence electrons & they’re transferred to a nonmetal; the nonmetal GAINS electrons

• metals lose electrons to become cations (and attain the octet rule)

• nonmetals gain electrons to become anions

covalent compounds

formed between nonmetals; electrons are shared

octet rule

ionic compounds lose electrons to fulfill this rule, where the outermost energy level acquires 8 electrons 

covalent compounds gain electrons to fulfill this rule

ex) 1s² 2s² 2p⁶ 3s¹  will lose electron in 3s1 so that energy level n=2 has all 8 electrons 

overall net charge

when electrons are gained/lost, we add the protons + electrons to find the ___.

It is written as an exponent on an element.

Ex) Na⁺¹ (+1 is overall net charge here)

• can be solved using periodic table group # (all p.t. elements have neutral charge, so gaining/removing electrons will decrease/increase the net charge)

• Ex) Group 1A metal will LOSE 1 electron, resulting in 1+ net charge 

• Group 2A metal will LOSE 2 electrons, resulting in 2+ net charge

• Ex) Group 6A nonmetal will GAIN 2 electrons, resulting in 2- net charge 

• Group 7A nonmetal will GAIN 1 electron, resulting in 1- net charge 

ionic formula

the total number of positive charges MUST equal the number of negative charges 

• the sum of ionic charges in the formula should equal 0

transition metals

include elements that can form more than one charge when they combine with anions to produce IONIC compounds

• the charge of transition metals in a compound is indicated by roman numerals in parentheses when naming them

polyatomic ions

these are a group of nonmetal atoms bonded together but have a SINGLE CHARGE.

*memorize table and know how to write formulas

molecular compound

formed only by NONMETALS that share electrons

• atoms can form these by satisfying the octet rule

(bonus: what is the bond between shared electrons called?)

covalent bond

bcuz the nucleus has protons and the outside of atoms have electrons, there is attraction between atoms. This attraction brings atoms close TOGETHER until they SHARE ELECTRONS, forming __. 

• the pairing of electrons

• a single line on a lewis dot diagram

(Ex. in the H2 molecule, a __ forms as H atoms move closer together. Each H atom will share its electron to become a stable molecular compound with a DUET configuration)

duet

each H atom is stabilized or surrounded by 2 electrons

(add pic from her notes)

lone pair electrons (nonbonding electrons)

• no boron examples

bonding electrons

electronegativity

An atom's ability to attract shared electrons in a chemical bond; higher electronegativity value = the stronger the pull of shared elections by the nucleus.

TREND on periodic table:

going DOWN the periodic table, electronegativity decreases

going ACROSS the periodic table, electronegativity increases

polarity of bonds

in a bond, the atom with a higher electronegativity value will have shared electrons gravitating towards the more electronegative atom. so the shared electrons gravitate more towards the stronger electronegative atom, spending more time there. bc of this , the electron density of a higher electronegative atom is higher

• the difference in electronegativity of bonding atoms can be used to predict the ______

in a bond, this means electrons are spending more time near the more electronegative atom

in this pic, this means chlorine is more electronegative

this symbol shows that as electrons move away from the less electronegative atom, the atom gets LESS electronegative (or slightly more positive)

dipole

is created when one end of the bond becomes slightly more positive and the other becomes slightly more negative

polar covalent bond

a bond with dipoles

Know Table 6.15 Electronegativity Differences and Types of Bonds

arrow

an arrow can be used to show electrons moving toward the more electronegative atom. There is a line in the arrow, making a positive sign over the less electronegative atom that is more positive

nonpolar covalent bonds are __

atoms are HYDROPHOBIC. DOesnt mix well with water (they are watetr-farin)

polar covalent bonds are ___

atom AS HYDROPHILLIC and interacts with water.

• bond in H20 are always polar covalent.

water (charged)

the bonds in water are polar covalent. water has charged bonds; this allows water molecules to interact with charged ends of other polar covalent molecules

• water can be interacted with by IONIC AND POLAR COVALENT OUDNS@

Combination reaction

two or more elements form one product.

• simple compounds combine to form one product.

Decomposition reaction

one substance splits into

two or more simpler substances.

Single replacement reaction

one element takes the

place of a different element in another reacting compound.

double replacement reaction

positive ions in the reacts compounds switch places

combustion reaction

oxidation

reduction