Chapter 3 Quiz Study

• dalton atom created the hook and eye arrangement

• dmitri mendeleev created the first design of the periodic table

• mendeleev also created a periodic repetition

  • superscript is atomic number

  • subscript is the elemental number

• thompson atom created the pudding model

• he also discovered the electron

• ernest Rutherford introduced the nuclear model

  • nucleus - center of the atom .. dense with + charge

  • electron cloud - with - charge

• bohr atom described the atom to have a similar structure to the solar system orbit

• nucleus is positively charged and surrounded by negatively charged electrons

Question

1. greeks thought atoms were made up of what four elements? - air, fire, water, earth

2. whose atom had the hook and eye? - dalton

3. who discovered the periodic table? - mendeleev

4. whose atom looked like pudding? - thompson

5. who described the current model of an atom? - bohr atom

• particle accelerators are being used today

• electron - negative chatge .. floats around

• proton - positively charged .. lives in nucleus

• neutron - neutrally charged .. lives in nucleus

• elections = 9.1 ×10^-31 kg

• protons = 1.673 × 10^-27

• neutrons = 1.675 × 10^-27

• an atom is mostly empty space

• electrons are grouped into shells

• neutral atom: # of protons = # of electrons

• # if protons determines the chemical element of the atom

• closer to the nucleus the stronger the binding energy … K has the strongest binding energy while Q has the weakest

• normal state of an atom is electrically neutral and the charge is zero

• if an atom has an extra electron or has had an electron removed is it ionized

• each shell is where “n” is the shell # .. 2n²

• K=1 .. L=2 .. M=3 .. N=4 .. O=5 .. P=6 .. Q=7

• # of electrons in the outermost shell is equal to its group in the periodic table

• # of electron shells is equal to its period in the periodic table

• no outer shell can obtain more then 8 electrons

Questions

1. what is the maximum number of electrons that can exist in the O shell?

   1. 2n² .. 2(5)² .. 2(25) .. = 50 electrons

2. How many can exist in the M shell?

   1. 2n² .. 2(3)² .. 2(9) .. = 18 electrons

• centricipetal force - center seeking force .. keeps electron in orbit .. trying to get toward

• centrifugal force - maintains distance from the nucleus .. trying to get away

• closer the electron is to the nucleus the stronger the binding energy

• chemical symbol = alphabetic abbreviation

• the atomic number = protons = the atomic # represented by Z (subscript)

• atomic mass = # of protons + # of neutrons (A)

• elemental mass (amu) rarely a whole number

• atomic mass always a whole number

• atomic mass # & precise mass of an atom is NOT equal

• atomic mass # is. whole number that Is equal to the number of nucleons in the atom

• atoms of various elements may combine to form structures called molecules

• a chemical compound is any quantity of one type of molecule

• atoms combine with each other to form compounds in two main ways : covalent and ionic

• covalent bonds : sharing of electrons

• ionic bonds : transfer of an electron from one atom to another

• radioactivity : spontaneous emission of particles and energy in order to become stable

• elements that have radioactive isotopes are radioisotopes

• beta emission = electron is created in the nucleus .. then ejected w/ considerable kinetic energy and escapes the atom

  • results in a small loss of mass and one unit of negative electric charge from the nucleus

• increasing the atomic # by one

  • atomic mass remains the same

• alpha emission = emits alpha particle .. consists of 2 protons and 2 neutrons bound together w/ an atomic mass of 4 .. chemically different after the change .. nucelus is down 4 amu

• radioactive half life = the time required for a quantity of radioactivity to be reduced to one half its original value

  • never quite reaches zero

  • use the radioactive decay law (T 1/2) .. (original x 1/2) .. JUST KNOW THERE IS A LAW

  • varies from less than a second to many years

• ionizing radiation can be put into 2 categories Particulate and Electromagnetic

• differences between the two are mass .. energy .. velocity .. charge .. origin

• particulate radiation = two types .. alpha particles and beta particles .. alpha are large and exert great electrostatic force .. emitted only from the nuclei of heavy elements .. travels w/ high velocity and transfers is kinetic energy to orbital electrons of other atoms .. beta originate in the nuclei or radioactive atoms .. light particles w/ an atomic mass of 0 .. travels much faster and ionizing several hundreds of atoms per centimeter

• electromagnetic radiation = x-rays and gamma rays .. speed of light = 3.0 × 10^8 meters per second

• unlimited range in matter - loses intensity but never really reaches zero

• x-rays are produced outside the nucleus in electron shells

• gamma rays are inside the nucleus .. come from the nucleus of a radioisotope w/ alpha and beta emission