the atom & subatomic particles. atomic number atomic number: = size of nuclear charge = size of...
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Atomic NumberAtomic Number
atomic number:atomic number: = size of nuclear charge= size of nuclear charge = number of protons in nucleus= number of protons in nucleus determines identity of elementdetermines identity of element used to give order to periodic tableused to give order to periodic table
For neutral atoms:For neutral atoms: atomic number = number of electronsatomic number = number of electrons
Number of Protons = Number of ElectronsNumber of Protons = Atomic NumberAtomic Mass = Protons + Neutrons
What we knew by 1932:What we knew by 1932:
1.0087 amu1.0087 amu
(or 1 amu)(or 1 amu)
00Neutron, Neutron, 11nn
1.0073 amu1.0073 amu
(or 1 amu)(or 1 amu)
+1+1Proton, Proton, 11p or p or 11HH
.0005486 amu.0005486 amu
(or 0 amu)(or 0 amu)
-1-1Electron, Electron, 00ee
Relative MassRelative MassRelative ChargeRelative Charge
-1-1
11 11
00
Location of Subatomic ParticlesLocation of Subatomic Particles
• Electrons located Electrons located outsideoutside nucleus nucleus
• Protons & neutrons located Protons & neutrons located insideinside nucleus nucleus
• Protons & neutrons = nucleonsProtons & neutrons = nucleons
IsotopesIsotopes
atoms of same element with atoms of same element with
different # neutronsdifferent # neutrons (mass # is different) (mass # is different) # protons stays same! (atomic # is same)# protons stays same! (atomic # is same)
DaltonDalton’’s theory modified in number of s theory modified in number of important ways:important ways: the atom is divisible (the atom is divisible (protons, neutrons, electrons)protons, neutrons, electrons) atoms of same element can be different (atoms of same element can be different (different different
# neutrons# neutrons))
NotationNotation
1212CC66
•left left superscriptsuperscript is is mass numbermass number
•left left subscriptsubscript is is atomic numberatomic number
NotationNotation
1212CC66
12 = # protons + neutrons12 = # protons + neutrons 6 = # protons6 = # protons
12 – 6 = 6 neutrons12 – 6 = 6 neutrons
How many neutrons in this How many neutrons in this atom?atom?
1717OO88
Mass number is ?Mass number is ?
Atomic number is ?Atomic number is ?
# of neutrons is ?# of neutrons is ?
# of electrons in atom is?# of electrons in atom is?
1717
88
17 – 8 = 917 – 8 = 9
88
Mass number is ?Mass number is ?
Atomic number is ?Atomic number is ?
# of neutrons is ?# of neutrons is ?
# of electrons in atom is?# of electrons in atom is?
1515
NN77
1515
77
15 – 7 = 815 – 7 = 8
77
Mass number is ?Mass number is ?
Atomic number is ?Atomic number is ?
# of neutrons is ?# of neutrons is ?
# of electrons in atom is?# of electrons in atom is?
19 19 FF
1919
99
19 – 9 = 1019 – 9 = 10
99
Other NotationsOther Notations Might also see: C-Might also see: C-1212
number following symbol is number following symbol is mass numbermass number!!
Need to look up atomic numberNeed to look up atomic number
WhatWhat’’s the difference between s the difference between H-1, H-2, and H-3H-1, H-2, and H-3??
All HAll H’’s have 1 protons have 1 proton
H-1: mass # = 1 H-1: mass # = 1 1 proton, 0 neutrons1 proton, 0 neutrons
H-2: mass # = 2 H-2: mass # = 2 1 proton, so it must have 1 neutron1 proton, so it must have 1 neutron
H-3: mass # = 3 H-3: mass # = 3 1 proton, so it must have 2 neutrons1 proton, so it must have 2 neutrons
Consider U-234, U-235, & U-238Consider U-234, U-235, & U-238
WhatWhat’’s the atomic number of U?s the atomic number of U? How many protons in U?How many protons in U? How many neutrons in U-234?How many neutrons in U-234? How many neutrons in U-235?How many neutrons in U-235? How many neutrons in U-238?How many neutrons in U-238? How many electrons in U?How many electrons in U?
9292
9292234 – 92 = 142234 – 92 = 142
235 – 92 = 143235 – 92 = 143
238 – 92 = 146238 – 92 = 146
9292
How many neutrons in Po-217?How many neutrons in Po-217?
WhatWhat’’s the atomic number?s the atomic number?
How many protons?How many protons?
So the neutrons are …So the neutrons are …
8484
8484
217 – 84 = 133 neutrons!217 – 84 = 133 neutrons!
IONSIONS
Atoms: electrically neutral so ...Atoms: electrically neutral so ...
# electrons = # protons# electrons = # protons IONS = atoms that gained or lost IONS = atoms that gained or lost electronselectrons protons and electrons aren't = anymore, so ions protons and electrons aren't = anymore, so ions
are are not not neutral they carry a charge (+/-)neutral they carry a charge (+/-)
IONSIONS
Charge of ion: = # protons minus # Charge of ion: = # protons minus # electrons electrons
(subtract the electrons since are negative)(subtract the electrons since are negative)
IONSIONS
If atom loses electrons, it has more If atom loses electrons, it has more positive charge than negative positive charge than negative What kind of ion is it?What kind of ion is it?
If atom gains electrons, it has more If atom gains electrons, it has more negative charge than positive negative charge than positive What kind of ion is it?What kind of ion is it?
positivepositive
negativenegative
Charge of IonsCharge of Ions
Ion chargeIon charge written as written as right superscriptright superscript ClCl-1-1 a chloride ion with a charge of -1a chloride ion with a charge of -1 NaNa+1+1 a sodium ion with a charge of +1a sodium ion with a charge of +1 OO-2-2 an oxygen ion with a charge of -2an oxygen ion with a charge of -2
If no right superscript, itIf no right superscript, it’’s understood to s understood to be zero and therefore a neutral atombe zero and therefore a neutral atom
Putting it all togetherPutting it all together
How many protons, neutrons, & electrons How many protons, neutrons, & electrons in each of the followingin each of the following
2323NaNa+1+1
11
2525MgMg+2+2
1212
3434SS-2-2
1616
6464ZnZn+2+2
3030
11 p, 12 n, 10 e11 p, 12 n, 10 e
12 p, 13 n, 10 e12 p, 13 n, 10 e
16 p, 18 n, 18 e16 p, 18 n, 18 e
30 p, 34 n, 28 e30 p, 34 n, 28 e
Lost Lost 11
Got 2Got 2
Lost Lost 22
Lost Lost 22
What is an amu?What is an amu?
equal to the atomic mass unitequal to the atomic mass unit
amu amu 1/12 the mass of the C-12 atom 1/12 the mass of the C-12 atom
C-12 is used as the reference for atomic massC-12 is used as the reference for atomic mass
Atomic Weight or MassAtomic Weight or Mass
Atomic mass is relativeAtomic mass is relative 11stst H-1 used as standard: H-1 used as standard:
1 atom of H = 1 amu1 atom of H = 1 amu next O-16 used as standard:next O-16 used as standard:
O combines with many elementsO combines with many elements 1 atom of O = 16 amu's1 atom of O = 16 amu's
Now C-12 is the standard:Now C-12 is the standard: 1 atom of C-12 has a mass of exactly 12 amu's1 atom of C-12 has a mass of exactly 12 amu's