Atomic and Molecular Structure Flashcards
(36 cards)
Atom
the basic building block of matter, representing the smaller unit of a chemical element
Nucleus
formed by the protons and neutrons, it is the core of an atom
Orbitals
this is where the electrons are and is located outside of the nucleus
Elements
- composed of very small particles called atoms
- identical in size, mass, and chemical properties
Compounds
-composed of atoms of more than one element
Chemical Reaction
involves only the separation, combination, or rearrangement of atoms
Protons
- carry a single positive charge and have a mass approximately one unified atomic mass unit (amu or u)
- amu is equivalent to one dalton
Atomic Number (z)
equal to the number of protons found in an atom of that element
Neutrons
-carry no charge and have a mass only slightly larger than that of protons
Electrons
- carry a charge equal in magnitude but opposite in sign to that of protons
- has a very small mass
Valence Electrons
- shell furthest from the nucleus
- the farther the valence electrons are from the nucleus, the weaker the attractive force of the positively charged nucleus and the more likely the valence electrons are to be influenced by other atoms
Mass Number (A)
- equal to the total number of nucleons (protons and neutrons)
- mass number (A) = number of protons + number of neutrons
Molecular Weight
the weight in grams per molecule per one mole of a given element (g/mol)
Mole
is a unit used to count particles and is represented by Avogadro’s number (6.02x10^23)
Isotopes
atoms with the same number of protons but different numbers of neutrons
-ex: 14 C 6 has 6 protons and 8 neutrons
Standard Atomic Weight
a weighted average of all the isotopes of an element found naturally on Earth
Example Problem (isotopes)
Element Q consists of three different isotopes, A, B, nad C. Isotope A has an atomic mass of 40 u and accounts for 60% of naturally occurring Q. The atomic mass of isotope B is 44 u and accounts for 25% of Q. Finally, isotope C has an atomic mass of 41 u and a natural abundance of 15%. What is the atomic weight of element Q?
0.60(40u) + 0.25(44u) + 0.15(41u) = 24 u + 11 u + 6.15 u = 41.15 u
The atomic weight of element Q is 41.15 g/mol
Quantum Theory
- energy emitted as electromagnetic radiation from matter comes in discrete bundles called quanta
- Energy value of a quantum is calculated by the equation: E=hf , h= Planck’s constant 6.626 x 10-34 Js, f= frequency
The Bohr Model
E= -Ry/n^2 , Ry = 2.18x10^-18
Electromagnetic Energy
E= hc/lambda, c= 3.0x10^8 m/s
Line spectrum
each line on the emission spectrum corresponds to a specific electronic transition
Balmer series
-four wavelengths in the visible region , n>2 to n=2
Lyman series
-higher energy transitions into the UV region
n>1 to n=1
Orbital
- a representation of the probability of finding an electron within a given region
- a specific region within a subshell that may contain no more than two electrons