review of atomic model. key words subatomic particle energy levels atomic mass protonisotope...
Post on 22-Dec-2015
215 Views
Preview:
TRANSCRIPT
Review of Atomic Model
Key Words
subatomic particle energy levels
atomic mass proton isotope
electron neutron ion
atomic mass unit (u) atomic number
Elements are pure substances containing one type of atom – found on the Periodic Table.
The atom is the smallest part that retains all the properties of that element.
protons (p+) neutrons (no) electrons (e-)
Charge
Mass
Location
+1.6 x 10-19 C 0 -1.6 x 10-19 C
1.67 x 10-24 g 1.67 x 10-24 g 9.11 x 10-28 g
Nucleus Nucleus Orbit clouds
The atomic number (Z) is the number of protons in the nucleus of an atom - identifies an element.
The atomic mass (A) is the number of protons plus the number of neutrons.
H : the hydrogen atom
H+ : a positively charged hydrogen ion H- : negatively charged
hydrogen ion
Ion: an atom that has gained or lost electrons.
Results in a negative or positive charge equal to the electrons transferred.
Neutral: an atom with the same number of protons and electrons – cancelled charges.
Deuterium Atomic Mass = 2
Atomic Number = 1
Hydrogen Atomic Mass = 1
Atomic Number = 1
Isotopes: Atoms with the but a different number of neutrons.
Atomic mass is actually an average of isotopes of an element based on relative abundance in nature.
same number of protons
Mass spectrometer determines the mass of individual atoms or isotopes.
Sends atoms through a magnetic field which bends their paths.
The heavier the atom – the less it bends.
Potassium isotopes:
1. 19 protons and 20 neutrons - mass number of 39(potassium-39 39K)
2. 19 protons and 21 neutrons - mass number of 40 (potassium-40 40K)
3. 19 protons and 22 neutrons - mass number of 41 (potassium-41 41K)
Magnesium exists as three isotopes in the world:
78.99% is 24Mg (23.985 μ)10.00% is 25Mg (24.986 μ)11.01% is 26Mg (25.982 μ)
(0.7899)(23.985 μ) = 18.95 μ
(0.1000)(24.986 μ) = 2.499 μ
(0.1101)(25.982 μ) = 2.861 μ
= 24.31 μ +
Calculate the average atomic mass of magnesium:
helium 5He 6He
The nucleus of some isotopes are unstable and break apart over time - radioactivity.
Radioisotopes - unstable nuclei releasing energy and/or particles.
Release of energy is called radioactive decay.
Atom may be converted into another isotope or a completely different element.
Half-life - amount of time it takes for half the radioisotope to be converted into another particle.
Many different types of decay: alpha decay, beta decay, gamma decay
• Isotopes - differ in mass because they have different numbers of neutrons.
• Relative / percent abundance is the fraction of each isotope found in an average sample of the element.
top related