Unit 3: atoms and the periodic chart Flashcards
proton
a positively charged particle in the nucleus
symbol: p+
neutron
a neutral particle (has no charge) in the nucleus
symbol: n0
electron
a negatively charged “particle” outside the nucleus
(actually more of a wave than a particle)
symbol: e-
ion
a charged atom or molecule
Examples: Na+, OH-, Al+3
cation
a positively charged atom or molecule
Examples: Na+, NH4+
anion
a negatively charged atom or molecule
Examples: Cl-, SO4-2
isotope
one type (weight) of an element
A difference in the number of neutrons
Examples: carbon-12 and carbon-14
atomic mass
a weighted average of the naturally occurring isotopes of an element
the bigger number on the periodic chart, with decimals
protons + # neutrons = atomic mass
How do you find the number of electrons?
find the atomic number and adjust for the charge
Example: F-
atomic number 9 + 1 extra electron = 10 e-
atomic number
the number of protons
the smaller number on the periodic chart
a whole number
How do you find the number of protons?
Look at the element’s atomic number.
How do you find the number of neutrons?
Subtract the atomic number from the atomic mass.
Rutherford’s experiment
Shot alpha particles (helium nuclei) at a thin piece of gold foil. Some particles went straight through, others were deflected. Demonstrated that atoms are mostly empty space with a dense core (nucleus). Disproved the plum pudding model.
Bohr’s experiment
He electrified hydrogen gas until it glowed then separated the light with a prism. Demonstrated that there are particular wavelengths of light being given off, which is characteristic of the element. The atomic spectrum shows how much energy is released by the excited electrons falling back down to the ground state.
Which atom has the larger atomic radius, Ca or Ca+2?
Ca
They have the same number of protons. Ca has two more electrons, which makes its electron cloud larger.
Which atom has the larger atomic radius, F- or Na+?
F- They have the same number of electrons (10).
F has 9 protons and Na has 11. More protons pull in the electron cloud more, which makes Na+ the smaller atom.
alpha decay
A radioactive atom breaks apart into two atoms, a helium nucleus (2 protons and 2 neutrons) and the left overs.
beta decay
A radioactive atom breaks apart into an atom and an electron. One of the neutrons splits into a proton and an electron.
4 sources of the elements
1-4 Big Bang
5-26 stellar fusion (the star’s life)
27-92 super nova (star death)
93+ man made
alkali metals
first column
+1 charge
float
react with water
form bases
alkali earth metals
second column
+2 charge
not as reactive as alkali metals
transition metals
middle of the periodic chart
very stable (gold, silver, copper)
bright colors (sapphire, ruby, emerald, paint, etc)
can be +1, +2, or +3 charges
metals
low electronegativity
good conductors of heat and electricity
malleable and ductile
form cations
nonmetals
high electronegativity
gasses or brittle solids
poor conductors
form anions