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HS Chem Atomic Structure and the Mole
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19
Chemistry
10th Grade
11/11/2012

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Term
Democritus 460-370 BC
Definition
-everything is made up or indivisible particles
-came up with concept of atoms
-did not have a scientific method of proving his idea
Term
Dalton 1766-1844 (1800)
Definition
-father of modern atomic theory
-matter is made of indivisible atoms
-atoms of a element have the same mass
-atoms can combine in whole number ratios
-atoms can only combine, separate, or rearrange in chemical reaction
Term
Electron (1880's)
Definition
-outside of nucleus
-negative charge (minus one charge)
-symbol e-
-mass is 1/1840 of an amu/proton
Term
Proton (1890's)
Definition
-resides in nucleus
-positive charge (plus one charge)
-symbol p+
-mass is 1 atomic mass unit (amu)
Term
Neutron (1930)
Definition
-in nucleus
-no charge
-symbol n0
-Mass is 1 amu (last to be discovered)
Term
Thomson 1900
Definition
plum pudding model-protons and electrons are scattered evenly throughout atom
Term
Rutherford 1871--1937 (1911)
Definition
Gold foil experiment- gold hit by alpha particles that are radioactive and 4x heavier than proton. Most went straight through but some deflected.
Theory- an atom is mostly empty space but the nucleus is positive because of protons, electrons are on outside
Term
Nucleus
Definition
-contains protons and neutrons
-very dense
-very small and heavy
-99.9% of the mass of an atom
-very small amount of the volume
Term
Electron Cloud
Definition
-area where electrons travel
-made of mostly empty space
-the # of protons in an atom equals the # of electrons in same atom
-charge of total atom is neutral because protons and electrons cancel
Term
Atomic number
Definition
# of protons = number of electrons= blue # pd table on the wall
(protons identify element)
Term
Atomic mass
Definition
(as mass increases so does number)
-weight of 1 atom in amu, includes proton and neutrons
-protons and neutrons each weight 1 amu
-electrons weigh nothing
Term
Mass number
Definition
sum of particles in the nucleus, the protons, and neutrons, don't count electrons because they don't weigh
Term
Mass #
Symbol
At.#
Definition
1 35
H Cl
1 17

The top number is the mass #= protons+neutrons
The bottom number is the Atomic #= protons= electrons
To find neutrons =mass#-atomic #
Term
How much mass, atomic number, protons, neutrons, electrons

32
S
16
Definition
mass-32
atomic number-16
protons-16
neutrons- 16
electrons-16
Term
Isotopes
Definition
(all atoms have protons=electrons)
an atom that differs from another of the same element is because of the # of neutrons
H-1 weigh 1amu
H-2 weighs 2amu
H-3 weighs 3amu
The mass on pd table is avg of isotopes
Term
Average atomic mass
Definition
the avg mass based on percent abundance of all existing isotopes of an element
Example-
Chlorine- 35(76%)=35*.76=26.6
Chlorine- 37(24%)=37*.24=8.88
Avg Chlorine=26.6+8.88=35.48amu
Term
The mole(mol)
Definition
-contains 6.02*10^23 particles
-also called avogrados number (after scientist)
-unit used to measure particles in a substance
-1 mol= 6.02*10^23=mass(g) from pd table
Term
Unit mol hints
Definition
-always pairs with one
-g and amu always pair with mass from pd table
-atom usually pairs with 6.02*10^23 (mols or grams) or the number one (amu)
Term
Examples
Definition
Moles? form 60.9g of Mg
60.9 X 1 mol =2.5 mol
-------
24.3g

Grams? in 1.2*10^24 atoms of Cl
1.2*10^24 X 1 mol X 35.5g = 70g
------ ------
6.02*10^23 1 mol
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