atomic structure Flashcards
what is an atom
the smallest part of an element
what are the models in order
Dalton Model, Plum Pudding Model, Rutherford Model, Bohr Model, Quantum Model
what is dalton’s atomic theory
- all matter is composed of small particles called atoms which cannot be subdivided, created or destroyed
- atoms of an element are identified in their physical or chemical element
- atoms of different elements differ in their physical or chemical properties
- atoms of different elements combine in simple whole number ratios to form compounds
- in chemical reactions, atoms are combined, separation or rearranged, but never created or destroyed
changes to Dalton’s theory
- atoms can be subdivided , created and destroyed ( atomic bomb, man made elements)
- atoms of the same element are NOT identical (isotopes)
what does Dalton’s model show
that atoms are tiny particles with no internal structure
what is the Plum pudding model
-1904, Thompson disproved Dalton’s model of the atom
how did Thompson discover the electron
used a cathode ray tube (CRT)
what does the Plum Pudding model show
that negatively charged particles balance the positively charged particles to make atom neutral
what is the Rutherford model
in 1911, Rutherford disproved Thompson’s Plum Pudding model
how did Rutherford disprove Thompson’s Plum Pudding Model
he shot positively charged particles at a thin foil of god (Gold foil experiemnt)
what does the Rutherford model show that
- the nucleus is small and positive because few positively charged particles were deflected
- the electron cloud is large and negative because many positively charged particles penetrated
- most of the mass is in the nucleus
- most of the atom is empty space
Bohr model
-in 1913, Bohr said electrons travel around the nucleus in specific energy levels
why is the Bohr model incorrect
because it is difficult to pinpoint fast moving electrons
what is the quantum model
in 1926 a present day model of the atom shows electrons have wavelike properties and are somewhere in the electron cloud
what are the atom parts
the nucleus and electron cloud
the nucleus
- in the center
- smallest region
- positively charged
- has most of the mass
the electron cloud
- the outer region
- largest region
- negatively charged
- mostly empty space
where is proton found
nucleus
charge of proton
positive
symbols of proton
1+ or +
p+ or p
what is the mass of a proton
1.673 x 10-27kg
location of neutron
nucleus
charge of neutron
no charge
symbols for neutron
0 or n
mass of neutron
1.675 x 10-27 kg
location of electrons
electron cloud
charge of electron
negative
symbols of electron
1- or -
e- or e
mass of electron
9.109 x 10-31kg
atomic number
- each element has different atomic number
- elements are arranged according to increasing atomic number
- reveals the number of protons
- also reveals the number of electrons ( if the element is neutral)
what is the mass number
sum of the protons and neutrons
round the average atomic mass to a whole number
neutron number
neutron number = mass number minus atomic number
what is an ion
an atom that gains or loses electrons
what is a cation
- an ion with a positive charge
- loses electrons
what is a anion
an ion with a negative charge
gains electrons
what is an isotope
- all have the same number of protons
- all have the same chemical behavior
- the mass number is different because the umber of neutrons is different
how are isotopes written
hydrogen-2
H-2
what is the average atomic mass
- decimal # on the periodic table
- it is calculated using all naturally occurring isotopes of an element
- keep all numbers after the decimal
- the unit is amu ( atomic mass unit)
what is the percent abundance
occurrence of an isotope in nature
one number after the decimal
the unit is %
