Ch 2 (bonds and chemistry)

atom

smallest unit of matter that retains all of the element’s chemical properties

nucleus

atom’s center and contains protons and neutrons

protons

positively charged, weighs about 1.67×10^-24 g

neutron

uncharged, weighs about 1.67×10^-24 g

electron

negatively charged, smaller in mass, weighs about 9.11×10^-28 g

atomic number

determined by the number of protons

mass number

determined by the number of protons and neutrons

atomic mass

calculated mean of the mass number for its naturally occuring isotopes

energy

capacity to cause change

potential energy

the energy that matter possesses because of its location or structure

chemical equilibrium

reached when the forward and reverse reaction rates are equal, the amounts of reactants and products are stabilized at a particular ratio, but are almost never equal

electronegativity is based on 3 things:

more protons, more electrons, more distance of the outer electrons from the nucleus = more electronegativity

the more electronegative an atom

the more strongly it pulls shared electrons towards itself

covalent bond

• the sharing of a pair of valence electrons

• STRONG bond

true or false. there are single and double covalent bonds

true

nonpolar covalent bond

• atoms have similar electronegativities

• share the electrons

polar covalent bond

• atoms have different electronegativities

• share electrons unequally

hydrogen bond

forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom

order from least to most strength: ionic, hydrogen, van der waals, polar, nonpolar

van der waals, hydrogen, nonpolar, polar, ionic

van der waals interactions

occur when transiently positive and negative regions of molecules attract each other