Atomic Structure Flashcards
Isotopes
Atoms of the same element that differ in mass due to a different number of neutrons
John Dalton’s 4 Findings
- All atoms are composed of indivisible atoms
- All atoms of a given atom must be identical in every way
- Atoms of different elements must be different in some fundamental way
- Compounds are produced from a reaction between different atoms (elements)
Rutherford’s Experiment - 2 Observations
1) Most of the alpha particles passed through the gold foil
2) A few particles were deflected or back-scattered
Rutherford’s Experiment - 2 Conclusions
1) Most of the an atom is empty space
2) An atom contains a dense core with a positive charge
Proton
Location: Nucleus
Charge: +1
Mass: 1
Neutron
Location: Nucleus
Charge: 0
Mass: 1
Electron
Location: In orbitals outside the nucleus
Charge: -1
Mass: 0
Alpha particle
A charged helium nucleus
Beta particle
A high speed electron
Atomic number
The number of protons in an atom
Why is an atom electrically neutral?
The number of protons is equal to the number of electrons in an atom
Every element has a unique _____
Atomic number
Mass number
The number of protons plus the number of neutrons
Label parts: 11 5 B
Mass number: 11
Protons: 5
Atomic number: 5
Electrons: 5
Neutrons: 6
Word form: Boron - 11
Atomic mass
The weighted average of all naturally occurring isotopes of an element (decimal number)
How is the atomic mass of an element determined?
- Convert the percent abundances to a decimal (move decimal point two places to the left)
- Multiply the mass number by the converted percent abundance
- Add all the products
2 facts about atomic mass
1) Should be somewhere between the two original masses
2) Should be closest to the mass of the most abundant isotope
Bohr model description
Electrons revolve around the nucleus in one of seven shells or rings called potential energy levels (PELS). The rings correspond to rows or periods of the periodic table.
Compare the energy of electrons closest to the nucleus to the energy of electrons farthest from the nucleus
Close to nucleus = lowest energy
Farthest from nucleus = highest energy
What is the maximum number of electrons each PEL can hold?
1 - 2 electrons
2 - 8 electrons
3 - 18 electrons
4 to 7 - 32 electrons
What is the shortcoming of the Bohr model?
It is only a 2-D representation
Valence electrons
Electrons in the outermost PEL
Noble gases (group 18)
Odorless, colorless, nonflammable gases that are inert due to a complete octet
Inert
Do not react