copyright©2000 by houghton mifflin company. all rights reserved. 1 the modern view of atomic...

The Modern View of Atomic Structure

electrons protons: found in the nucleus, they have a

positive charge equal in magnitude to the electron’s negative charge.

neutrons: found in the nucleus, virtually same mass as a proton but no charge.

The The atomatom contains: contains:

Figure 2.14 Nuclear Atom Viewed in Cross Section

The Mass and Change of the Electron, Proton, and Neutron

Particle Mass (kg) Charge

Electron 9.11 10 31 1

Proton 1.67 10 27 1+

Neutron 1.67 10 27 0

• Very dense nucleus containing almost all of the atom’s mass.

• Electrons constitute most of the volume of the atom. Electrons are involved when atoms combine or “bond” to form molecules.

• All atoms contain protons, electrons and neutrons

• Different atoms have different properties due to different #’s of protons, electrons and neutrons.

• Atomic number (Z) = # of protons

• Mass number (A) = # of protons + # of neutrons

ISOTOPES

• Atoms with the same # of protons butdifferent # of neutrons.

• Isotopes have almost identical chemical properties since they have the same # of electrons.

The Chemists’ Shorthand: Atomic Symbols

K Element Symbol39

Mass number

Atomic number

Figure 2.15Two Isotopes of Sodium

The Chemists’ Shorthand:Formulas

• Chemical Formula:• Symbols = types of atoms• Subscripts = relative numbers of atoms

• Structural Formula:

• O=C=O

• Atoms or groups of atoms that has a net positive or negative charge.

• Atoms either gain or lose electrons to acquire a charge.

Cation: A positive ionMg2+, NH4

Anion: A negative ionCl, SO4

Ionic Bonding: Force of attraction between oppositely charged ions.

Salt (Ionic solid): Solid consisting of oppositely charged ions.

Figure 2.19 Sodium Chloride

• Simple Ions: Na+

• Polyatomic Ions: Groups of covalently

bonded atoms that carry a charge.

Periodic TableElements classified by: properties

atomic number

Groups (vertical) 1 or 1A = alkali metals 2 or 2A = alkaline earth metals 17 or 7A = halogens 18 or 8A = noble gases

Periods (horizontal)

Alkali MetalsGroup 1 or Group 1A

Alkali Metals

• Group 1 or 1A• Metals with low mp• Soft enough to cut with a knife• Form +1 ions when reacting with non-

metals

Alkaline Earth Metals

• Group 2 or 2A

• Less reactive than Group 1

• Form +2 ions when reacting with non-metals

Halogens

• Group 17 or 7A or VII A

• Non-metals

• Form -1 ions when reacting with metals

Noble GasesGroup 18 or Group 8A

Noble Gases

• Group 18 or 8A or VIII A

• Single atom (monoatomic) gases

• Little reactivity

Metals, Nonmetals & Mettaloids

Metals

• Shiny/ metallic luster• Good conductor of heat & electricity• Malleability• Ductile• Tend to lose electrons

Non-Metals

• Brittle solids• Many gases at room temperature• Liquid – bromine• Poor conductors• Tend to gain electrons• Often share electrons with other non-

metals to form covalent bonds

Mettalloids

• Some characteristics of metals and some characteristics of non-metals.

• All are solids at room temperature• Semi-conductors of electricity.

• B, Si, Ge, As, Sb, Te, At

Transition Metals

Figure 2.21The Periodic Table

THE END!!!!!!!!!!

copyright©2000 by houghton mifflin company. all rights reserved. 1 the modern view of atomic...

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