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Introductory Chemistry, 3rd EditionNivaldo Tro
Intro to thePeriodic Table
And
AtomsVs.
IonsVs.
Isotopes
2
The Modern Atom
Atoms are composed of three particles - protons, neutrons and electrons
The nucleus contains protons and neutrons
The electrons move outside the nucleus
Neutral atom has same # protons and electrons.
3
+
+
The Nuclear Atom:
protons
neutrons
-
Nucleus
electrons
-
4
Subatomic Particles:
neutrons (n)
protons (p)
electrons (e)
Charge? Location?
5
Subatomic Particles:
0 nucleus
+1 nucleus
-1 outside
neutron
proton
electron
Charge? Location?
6
1
1
0 (1/1837)
neutron
proton
electron
Mass (amu)
Subatomic Particles:
7
Elements
Each element has a unique number of protons in its nucleus
Number of protons in the nucleus of an atom is called the atomic number– the elements are arranged on the Periodic
Table in order of their atomic numbers
Each element has a unique name and symbol– symbol either one or two letters
one capital letter or one capital letter + one lower case
8
How many?
protons = depends on element
neutrons = variable for each element
electrons = same as protons
9
atomic number -
The number of protons in one atom; each element has a different atomic number
The number on top of the element symbol in the periodic table
11
ReviewWhat is the atomic number of boron, B?What is the atomic mass of silicon, Si?How many protons does a chlorine atom have?How many electrons does a neutral neon atom have? Will an atom with 6 protons, 6 neutrons and 6 electrons be electrically neutral?Will an atom with 27 protons, 32 neutrons and 27 electrons be electrically neutral? Will a Na atom with 10 electrons be electrically neutral?
12
ReviewWhat is the atomic number of boron, B? 5What is the atomic mass of silicon, Si? 28.09 amuHow many protons does a chlorine atom have? 17How many electrons does a neutral neon atom have? 10Will an atom with 6 protons, 6 neutrons and 6 electrons be electrically neutral? YesWill an atom with 27 protons, 32 neutrons and 27 electrons be electrically neutral? YesWill a Na atom with 10 electrons be electrically neutral? No
Three Types of Elements
= Metal
= Metalloid
= Nonmetal
14
Metals
Solids at room temperature, except HgShinyConduct heat, electricityMalleable: can be shapedDuctile = drawn or pulled into wiresLose electrons and form cations (+ charge) in reactionsAbout 75% of the elements are metals
15
Nonmetals
Found in all 3 states
Poor conductors of heat & electricity
Solids are brittle
Gain electrons in reactions to become anions (- charge)Only a few on the right of periodic table
16
Metalloids
Show some properties of metals and some of nonmetals
Also known as semiconductors Properties of Silicon
shinyconducts electricity
does not conduct heat wellbrittle
17
The Modern Periodic Table
Elements with similar chemical and physical properties are in same column
Columns are called Groups or Families– designated by a number and letter at top
Rows are called Periods
Each period shows the pattern of properties repeated in the next period
18
The Modern Periodic Table
Main Group = Representative Elements = ‘A’ groupsTransition Elements = ‘B’ groups– all metals
Bottom rows = Inner Transition Elements = Rare Earth Elements– metals– really belong in Period 6 & 7
19
= Alkali Metals
= Alkaline Earth Metals
= Noble Gases
= Halogens
= Lanthanides
= Actinides
= Transition Metals
20
Important Groups - Hydrogen
nonmetal
colorless, diatomic gas– very low melting point & density
reacts with nonmetals to form molecular compounds– HCl is acidic gas– H2O is a liquid
reacts with metals to form hydrides– metal hydrides react with water to form H2
HX dissolves in water to form acids
21
Important Groups – IA, Alkali Metals
hydrogen usually placed here, though it doesn’t belongsoft, low melting points,low densityvery reactive, never find uncombined in naturetend to form water soluble compoundsreact with water to form basic (alkaline) solutions and H2 releasing a lot of heat
lithium
sodium
potassium
rubidium
cesium
22
Important Groups – IIA, Alkali Earth Metals
harder, higher melting, and denser than alkali metals
reactive, but less than corresponding alkali metal
form stable, insoluble oxides from which they are normally extracted
oxides are basic = alkaline earth
magnesium
calcium
beryllium
strontium
barium
23
Important Groups – VIIA, Halogens
nonmetals
F2 & Cl2 gases; Br2 liquid; I2 solid
all diatomic
very reactive
react with metals to form ionic compounds
HX all strong acids except HF
bromine
iodine
chlorine
fluorine
24
Important Groups – VIIIA, Noble Gases
all gases at room temperature, – very low melting and
boiling points
very unreactive, practically inert
very hard to remove electron from or give an electron to
25
Charged Atoms = Ions
Number of protons (atomic #) identifies the element!– all sodium atoms have 11 protons in the
nucleus
In chemical change, number of protons in nucleus of atom doesn’t change!
Atoms can lose or gain electrons becoming electrically charged, these are called ions
26
Ions
Atoms acquire a charge by gaining or losing electrons– not protons!!
Ion Charge = # protons – # electrons
ions with a + charge are called cations– more protons than electrons– form by losing electrons
ions with a – charge are called anions– more electrons than protons– form by gaining electrons
27
Atomic Structures of Ions
Metals form cationsFor each positive charge the ion has 1 less electron than the neutral atom– Na atom = 11 p+ and 11 e-, Na+ ion = 11 p+ and 10 e-
– Ca atom = 20 p+ and 20 e-, Ca2+ ion = 20 p+ and 18 e-
Cations are named the same as the metalsodium Na Na+ + 1e- sodium
ioncalcium Ca Ca2+ + 2e- calcium
ionThe charge on a cation can be determined from the Group number on the Periodic Table– Group 1A +1, Group 2A +2, (Al, Ga, In) +3
28
Atomic Structures of IonsNonmetals form anionsFor each negative charge the ion has 1 more electron than the neutral atom– F = 9 e-, F- = 10 e-
– P = 15 e-, P3- = 18 e-
Anions are named by changing the ending of the name to -ide
fluorine F + 1e- F- fluoride ionoxygen O + 2e- O-2 oxide ion
Charge on an anion can be determined by subtracting 8 from the Group number on the Periodic Table– Group 7A 7- 8 = -1; Group 6A 6 – 8 = -2
29
Example:
Find the number of protons and electrons in the Ca2+ ion.
30
Find the number of protons, electrons, & neutrons or the chagre in the following ions:
Na+, O2- , Cl 17 protons & 18 electrons, Nitrogen 7 protons & 10 electrons
31
Ion Charge & the Periodic Table
Charge on an ion can often be determined from an element’s position on the Periodic Table
Metals are always positive ions, nonmetals are negative ions
For many main group metals, the charge = the group number
For nonmetals, the charge = the group number - 8
32
Li+1
Na+1
K+1
Rb+1
Cs+1
Be+2
Mg+2
Ca+2
Sr+2
Ba+2
Al+3
Ga+3
In+3
O-2
S-2
Se-2
Te-2
F-1
Cl-1
Br-1
I-1
N-3
P-3
As-3
IA
IIA IIIA VIIAVIA
VA
Charges of Main Group Ions
C. Isotopes
Atoms of the same element with different numbers of neutrons.
C126
Mass #
Atomic #
¨ Isotope symbol:
“Carbon-12”
34
Isotopes
Isotopes = atoms of an element that have same # of protons but different # of neutrons
Isotopes of an element have different masses
isotopes are identified by their – mass numbers = protons + neutrons
All isotopes of an element are chemically identical– undergo the exact same chemical
reactions
35
Isotope Symbols• Cl-35 makes up about 75% of chlorine
atoms in nature, and Cl-37 makes up the remaining 25%
• Average atomic mass of Cl = 35.45 amu• Cl-35 has a mass number = 35, 17 protons
and 18 neutrons (35 - 17)
X = Atomic SymbolA = mass numberZ = atomic number
AXZ
Cl3517
or Cl-35
36
Example:
How many protons and neutrons in the chromium isotope
Cr5224
C. Isotopes
© Addison-Wesley Publishing Company, Inc.
C. Isotopes
Average Atomic Mass– reported on Periodic Table– weighted average of all isotopes
– Or multiply the relative abundance (%) by the mass of that isotope.
atoms of # total
atoms) of )(## (massatoms) of )(## (mass
Avg.AtomicMass
Avg.AtomicMass
C. Isotopes
EX: About 8 out of 10 chlorine atoms are chlorine-35. Two out of 10 are chlorine-37.
atoms 10
atoms) u)(2 (37atoms) u)(8 (3535.4 u
40
Neon
9.25%221210Ne-22
0.27%211110Ne-21
90.48%201010Ne-20
Percent Natural Abundance
Mass Number
Number of Neutrons
Number of ProtonsSymbol
Ne2010
Ne2110
Ne2210