2: Atoms Flashcards
Democritus
All matter is made up of very small particles
Atoms from atomos “not to cut”
Element
Substance that consists of identical atoms
Compound
Pure substance made up of two or more elements in a fixed ratio by mass
ELEMENTS IN THE HUMAN BODY
1. Big Four
C
H
N
O
ELEMENTS IN THE HUMAN BODY
2. Next Seven
Ca- strengthens bones; aids blood clotting
P- phosphates of bones, nucleic acids, energy transfer
K- regulate electrical balance of fluids; nerve conduction
S- component of proteins
Cl- necessary for growth and development
Na- regulate electrical balance
Mg- helps nerve and muscle action; present in bones
ELEMENTS IN THE HUMAN BODY
3. Trace Elements
Cr
Co
Cu
F
I
Fe
Mn
Mo
Zn
Mixture
Combination of two or more pure substances
Dalton’s Atomic Theory
- All matter is made up of tiny indivisible particles, atoms.
- All atoms of same element have same chemical properties.
- Compounds are chemical combination of different kinds of atom.
- Molecule is tightly bound combination of atoms that act as single unit
EVIDENCE FOR DALTON’S ATOMIC THEORY
1. Law of Conservation of Mass
-Antoine Lavoisier
-Matter can neither be created nor destroyed.
EVIDENCE FOR DALTON’S ATOMIC THEORY
2. Law of Constant Composition
-Joseph Proust
-any compound is always made up of elements in the same proportion by mass
Diatomic Elements
H
O
N
Cl
Br
I
F
Polyatomic
Ozone, O3
Phosphorus, P4
Diamond, millions of carbon atomd
Etc.
Atomic mass unit (amu)
-scale of relative masses of atoms
1 amu= 1.6605x10^(-24)
-mass exactly equal to 1/12 mass of one Carbon12 atom
Mass number
number of protons and neutrons in the nucleus of an atom
Atomic number
Number of protons in the nucleus of an atom
Isotopes
-Same number of protons but different number of neutrons; different atomic mass
-rejects second statement of Dalton’s atomic theory
Atomic weight
-Weighted average of the masses of the naturally occurring isotopes of the element
-unit: amu
Mendeleev (1860s)
-produced one of the first periodic tables
-arranging known elements according to increasing atomic weight
CLASSIFICATION OF METALS
1. Metal
An element that is solid, shiny, conducts electricity, ductile, malleable and forms alloy
CLASSIFICATION OF METALS
2. Nonmetal
-Element that does not have the characteristic properties of a metal and tends to accept electrons
-Graphite (form of carbon) is a nonmetal but conducts electricity (only exception)
CLASSIFICATION OF METALS
3. Metalloid
Element that displays some of the properties of both metal and nonmetal
Niels Bohr (1913)
-only certain values of kinetic energy of electrons are possible (energy levels); values inbetween are not permitted
-electrons in atoms do not move freely in space around nucleus; confined to specific regions called principal energy levels/ shells
Ground state electron configuration
The electron configuration of the lowest state of an atom
Principal energy level
An energy level containing orbitals of the same number
Shell
All orbitals of a principal energy level of an atom (1,2,3,4,5,6,7 etc)
Subshell
All of the orbitals of an atom having the same principal energy level and the same letter designation (s p d f)
Orbital
A region of space around nucleus that can hold a maximum of two electron (# of orbitals 1,3,5,7 for s,p,d,f respectively)
S orbitals
Sphere shape with nucleus at center
P orbital
Forms dumbbell shape
Electron configuration
A description of the orbitals of an atom or ion occupied by electrons
ELECTRON CONFIGURATION RULES
- Orbitals fill in the order of increasing energy from lowest to highest
- Each orbital can hold up to two electrons with spins paired
- When there is a set of orbitals of equal energy, each orbital becomes half-filled before any of them becomes completely filled.
Valence electron
Electron in the outermost occupied (valence) shell of an atom
Valence shell
The outermost occupied shell of an atom
Lewis dot structure
Symbol of the element surrounded by a number of dots equal to the number of electrons in the valence shell of an atom of that element
PERIODIC PROPERTIES
1. Atomic Size
-Determined by the size of its outermost occupied orbital
-increases from right to left, top to bottom; largest bottom left
PERIODIC PROPERTIES
2. Ionization energy
-energy required to remove the most loosely held electron from an atom in the gaseous state.
-always positive because energy must be supplied to overcome attractive force between electron and proton
-increases left to right, bottom to top; largest top right
-OPPOSITE TREND NI ATOMIC RADIUS
Monoatomic atoms
Only noble gases (exist in nature)
He
Ne
Ar
Kr
Xe
Rn
Molecules
-contain atoms of same element or atoms of two or more elements
(Unlike compounds na dapat two or more elements)
Allotropes
-one of two or more distinct forms of an element (i.e. Oxygen (O2) and Ozone (O3))
Mass spectrometer
-most direct and most accurate method for determining atomic and molecular masses
-gaseous sample is bombarded by a stream of high-energy electrons, producing positive ions; travels circular path with magnetic field
-amount of current generated is directly proportional to number of ions; determines the relative abundance of isotopes
