chemistry - unit 2: semester 1

democritus >

• came up with the concept of the atom

what does the word atom come from?

atomos

what does atomos mean?

indivisible or uncutable

dalton >

devloped the billard ball model

what is dalton called?

the father of atomic theory

daltons atomic theory >

• all matter is made of atoms and atoms are indivisible and indestructible spheres

• all atoms of a given element are identical in mass and properties

• compounds are formed by a combination of two or more elements

• a chemical reaction is a rearrangement of atoms

jj thomson >

discovered the plum pudding model

thomson proposed that what particles where stuck in the atom?

negative particles

how did thomson discover electrons?

cathode ray

what were the first subatomic particles discovered?

vacuum tube - all air has been pumped out

ernest rutherford >

conducted the gold foil experiment

what did rutherford discover?

the nucleus

is the nucleus positively or negatively charged?

positively

most of the _____ of the atom is concentrated in the nucleus

mass

is the nucleus tiny or big compared to the atom as a whole?

tiny

what is the atom mostly?

empty space

niels bohr >

discovered the planetary model

in the bohr model, electrons had a definite path toward where?

the nucleus

jame chadwick >

discovered the neutron

orbitals >

electrons exist in probability clouds called this

electrons are in constant ________

motion

do electrons orbit the nucleus in a circular pattern?

no

do we know the exact location of the electrons?

no

what are the four postulates of the modern atomic theory?

• all mater is made of atoms and they can only be destroyed by nuclear reactions

• atoms of the same element can be different (isotopes)

• atoms combine together to form compounds

• chemical reaction is a rearrangement of atoms

law of conservation of mass/matter >

mass is neither created or destroyed during a chemical reaction

what are electrons, protons and neutrons known as?

subatomic particles

what is the smallest particle of an element?

the atom

how do you find the atomic number?

the number of protons

the number of protons = the number of ___________

electrons

how do you get the mass number?

the sum of protons and neutrons

is the mass number give on the periodic table?

no

isotope >

atoms of the same element with different with different number of neutrons. it is a variation of the same element

why are atoms neutral?

because the number of electrons are always equal to the number of protons

a name or symbol of an element ____ followed by a number refers to the __________ in general

not, element

how do you find the average atomic mass?

(mass)(%) + (mass)(%)/100

valence electrons >

electrons located in the outermost energy level of an atom

what is the difference between an atom and an ion?

an ion forms when an atom gains or loses a electron during bonding and an atom does not gain or lose an electron

cations >

positively charged ions

how are cations formed?

when atoms lose valence electrons

in cations, do the atoms becomes more positive or negative?

positive

anions >

negatively charged ions

how are anions formed?

atoms gain valence electrons

in anions, does the atom become more positive or negative?

negative

are cations metal or nonmetals?

metals

are metals positive or negative?

positive

are nonmetals positive or negative?

negative

are anions metal or nonmetal?

nonmetal

what do cations and anions have in common?

they both have to do with valence electrons which are negatively charged particles

electron configuration >

the arrangement of the electrons in an atom

what does electron configuration represent?

the way electrons fill in the energy levels

how do electrons tend to arrange themselves? what is the called

at the lowest level possible, called the aufbau principle

what has the new atomic model suggested?

there are sublevels and orbitals within sublevels where electrons reside

what are the three different ways to show the arrangement of electrons?

• electron configuration

• orbital notation

• noble gas notation