Introductory Chemistry, 3 rd Edition Nivaldo Tro Intro to the Periodic Table And Atoms Vs. Ions Vs. Isotopes.

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

10

The Periodic Table of Elements

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