What is an atom
The smallest part of an element that has all of the elements properties
What are the three subatomic particles?
The proton, the neutron, the electron
Democritus
He discovered that the atom is the smallest piece of matter that is indivisible and that elements on the periodic table represent individual atoms
Dalton
-developed billiard ball model
4 principles to his theory
-matter is made of tiny indivisible particles (atoms)
-all atoms of an element are identical
-atoms of different elements behave differently
-atoms can be rearranged to form new substances in a chemical reaction
Thomson
Had the plum pudding model
-discovered electron
-said that atoms were positively charged with electrons spread throughout
-did an experiment with the cathode ray tube to discover the electron (device that produces and controls a beam of electrons inside a vacuum tube)
Rutherford
WHAT IS THE THING CALLED?
Using this experiment, he discovered that there is a positive dense electric field that alpha particles are hitting (nucleus)
- the centre is dense and positively charged (nucleus)
-most of the atom is empty space
He said that there could be a third particle type (we now know as the neutron) as the protons had a high atomic mass but did not account for the entire mass of the atom
Bohr
-Bohr said that electrons orbit the nucleus with a defined amount of energy
- they can jump to and from orbits=change in energy
-each orbit holds maximum number of electrons
Atomic mass unit
1amu=1.67x10^-1
Groups (rows) vs Periods (columns)
Groups:
1. Same number of valence e-
2. Valence shells increase by each step
Periods:
1. Same number of shells
2. Valence e- increase by each step
4 BEST KNOWN GROUPS
1 Alkali metals: soft, highly reactive, shiny, malleable, ductile
2 alkaline earth metals: light, shiny less reactive than alkali metals
3 halogen: very reactive reactive, reacts with alkali metals, has a colour each element
4 noble gases: very stable, inert (so they basically don’t undergo chemical reactions)
Atomic number
Tells us the number of protons (and electrons if the atom is neutral)
Mass number
The sum of all the particles in the nucleus (protons + neutrons)
Valence electrons
The number of electrons in the outer shell
Ion
A charged atom
Group 18 does not form ions
Isoelectronic
When you have the same number of electrons
Cation, anions, and who forms who
-Cations form when electrons are lost
-Anions form when electrons are gained
-Metals ten to form cations and non-metals tend to form anions
Isotope
Elements which the atoms have the same number of protons, but a different number of neutrons=different masses
Isotopic abundance
% of a given isotope in a sample of an element
MASS SPECTROMETER: Measuring instrument used to find the mass and abundance of isotopes
Radioisotope
An isotope that impulsively decays to produce two or more small nuclei
Ionization energy
The quantity of energy required to remove an electron from an atom or ion in the gaseous state
Electron afinity (need/want)
The change in energy that happens when an electron is added to a neutral atom in the GASEOUS STATE
Ionic radius
The measurement of the size of an ion (the distance from the center of the ion to the outermost electrons
DO WE NEED TO KNOW ATOMIC RADIUS FOR DIATOMIC ELEMENTS?
Effective nuclear charge
Nuclear charge: the total positive caarge of the nucleus
the overall electric force pulling the electron toward the nucleus
Shieding
When inner electrons block some of the nucleus’s pull on outer electron
