chapter 2 - atomic structure & radioisotopes

2.1 - elements & structure of the atom

matter

• pure substance → element or compound

  • element → atoms

  • compound → elements → atoms

• mixture → homogeneous or heterogenous

structure & properties of the atom

• protons (1+), neutrons (0), & electrons (1-)

  • electronic cloud - electrons on the outside (orbitals) & are being pulled towards nucleus

  • nucleus - protons & neutrons, have same amount to be a neutral atom, neutrons relieve the stress from so many protons

  • protons - 1.007 amu

  • neutrons - 1.008 amu

    • both determine the mass of an atom

  • electron - 0.00055 amu

• element

  • number of protons in contains → atomic number

  • ID of an element is given by the number of protons

  • every element has a 1 or 2 letter atomic symbol or chemical symbol

  • atomic symbol, atomic number, atomic mass → given on periodic table

  • protons + neutrons = mass of the atom

    • mass number → A

• isotopes

  • same element with same number of protons but different number of neutrons

  • all elements have their own unique percent natural abundance of isotopes

  • symbol notation

    • 

a) 17 protons, 18 neutrons, 18 electrons

b) 17 protons, 20 neutrons, 17 electrons

c) 19 protons, 19 neutrons, 22 electrons

d) 6 protons, 6 neutrons, 8 electrons

average atomic mass

• atomic mass of an element represents the average mass of the atoms that compose that element

• calcium-44 is heaviest bc it has most neutrons

• average mass closer to Ca-40 since it has the largest contribution (96.55%)

• average of A:

• 4 (1$) + 4($2) = 4 + 8 = 12/8 = 1.5

  4 + 4 8

• average of B:

• 1($1) + 9 ($2) = 1 + 18 = 19/10 = 1.5

• 1 + 9 10

• average: 24.23 × 36.97 + 75.77 × 34.97 / 100

• 895.7831 + 2649.6769 / 100

• 3545.46 / 100 = 35.45 amu

2.2 - navigating the periodic table

• 18 columns - groups

  • similar chemical & physical properties → noble gases, halogens, alkali metals (hydrogen is not a metal, react violently with water), alkaline earth metals (less reactive)

  • main groups or transition metals

• 7 rows - periods

metals, nonmetals, & metalloids

• metals

  • shiny, malleable, ductile

  • good conductors of heat & electricity

  • exist as solids at room temp except mercury (liquid)

• nonmetals

  • dull, brittle

  • poor conductors of heat or electricity → good insulators

  • exist as solids, gases & liquids at room temp

• metalloids or semi metals

  • have intermediate properties

  • between metals & nonmetals

important elements in biochem & medicine

• building block elements

  • hydrogen

  • carbon

  • nitrogen

  • oxygen

  • phosphorus

  • sulfur

• macronutrients

  • sodium

  • magnesium

  • potassium

  • calcium

  • chloride

  • phosphorus

  • sulfur

• micronutrients

  • iron

  • copper

  • zinc

  • iodine

  • fluoride

  • chromium

  • vanadium

  • molybdenum

  • selenium

  • silicon

2.3 - electron arrangement & valence electrons

• modern picture of the electron in an atom comes from quantum mechanics

• behavior of subatomic particles is not governed by the same physical laws as larger objects

  • describe the behavior of macroscopic objects

  • electrons are very small & light

• valence electrons

  • electrons in highest energy level of an atom

  • responsible for the chemistry

  • group 7 has 7 electrons, etc

2.4 - radioisotopes

• radioactive isotope (radioisotope)

  • has an unstable nucleus → all isotopes w atomic # > 82 are radioactive

  • undergoes decay to become more stable → spontaneous process

  • radiation emitted during decay

• radiation can be

  • subatomic particle or high energy particle

    • a - alpha particle

    • b - beta particle

  • electromagnetic radiation or high energy light wave

    • y - gamma ray

    • x ray

parent nuclide (unstable) → daughter nuclide + radioisotope

• alpha particle

  • slow-moving

  • high energy

  • 2 protons & 2 neutrons

  • +2 charge

• beta particle

  • high energy

  • electron

• most radioactive decay includes gamma rays

  • only energy

half-life

• time needed for ½ of the parent nuclides to decay into daughter nuclides