3.1 Properties of Matter 3.2 Changes in Matter 3.3 Mixtures of Matter
Atoms and Bonding The Building Blocks of Matter Matter may consist of elements, compounds, or...
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Transcript of Atoms and Bonding The Building Blocks of Matter Matter may consist of elements, compounds, or...
Atoms and Bonding
The Building Blocks of Matter
Matter may consist of elements, compounds, or mixtures.
Element: a substance made of only one type of atom
Compound: a substance made of two or more elements chemically bonded together.
Mixture: a physical combination of two or more pure substances (i.e., elements or compounds).
Atoms and Bonding
Atomic Theory and Models
Dalton thought that atoms were like smooth, hard balls that could not be broken into smaller pieces.
Atoms and Bonding
Atomic Theory and Models
Thomson suggested that atoms had negatively charged electrons embedded in a positive sphere.
Atoms and Bonding
Atomic Theory and Models
Rutherford was surprised that a few particles were deflected strongly. This led him to propose an atomic model with a positively charged nucleus.
Atoms and Bonding
Atomic Theory and Models
Through the first part of the twentieth century, atomic models continued to change.
Atoms and Bonding - Atoms, Bonding, and the Periodic Table
* Valence Electrons: the electron(s) in the outer shell of an atom’s electron cloud, which can combine with other atoms to form
molecules*The number of valence electrons in an atom of an element determines many properties of that element, including the
ways in which the atom can bond with other atoms.
Atoms and Bonding
The Periodic Table
Elements are organized into rows and columns based on their atomic number.
Atoms and Bonding
Periodic Table Activity
Click to open a browser window and access Active Art about the periodic table.
- Atoms, Bonding, and the Periodic Table
http://www.phschool.com/webcodes10/index.cfm?wcprefix=cgp&wcsuffix=1032&area=view&x=15&y=7
Atoms and Bonding - Atoms, Bonding, and the Periodic Table
The Periodic Table
As the number of protons (atomic number) increases, the number of electrons also increases. As a result, the properties of the elements change in a regular way across a period.
Atoms and Bonding - Atoms, Bonding, and the Periodic Table
The Periodic Table
The variety of colors in a “neon” sign results from passing an electric current through sealed glass tubes containing different noble gases.
Atoms and Bonding
Ions and Ionic Bonds
You and a friend walk past a market that sells apples for 40 cents each and pears for 50 cents each. You have 45 cents and want an apple. Your friend also has 45 cents but wants a pear.
Atoms and Bonding - Ionic Bonds
Ions and Ionic Bonds
When an atom loses an electron, it loses a negative charge and become a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.
Atoms and Bonding
Graphic Organizer
Attraction between oppositely charged ions
Feature Ionic BondPolar Covalent Bond
Nonpolar Covalent Bond
Metallic Bond
How Bond Forms
Charge on Bonded Atoms?
Example
Unequal sharing of electrons
Yes; positive or negative Yes; positive
O2 molecule
Equal sharing of electrons
Attraction between positive ions and surrounding electrons.
Yes, slightly positive or slightly negative
No
NaCl crystal (or other ionic compound)
H2O molecule (or other polar covalent molecule)
Calcium (or other metal)
Atoms and Bonding - Ionic Bonds
Ions and Ionic Bonds
Ions are atoms that have lost or gained electrons.
Atoms and Bonding - Ionic Bonds
Ionic bonding is the process of two or more atoms losing or gaining electrons to become charged ions. The charged ions are then attracted to each other:
Na + Cl -> Na+Cl-
Atoms and Bonding - Ionic Bonds
Properties of Ionic Compounds
In general, ionic compounds are hard, brittle crystals that have high melting points. When dissolved in water or melted, they conduct electricity.
Atoms and Bonding - Covalent Bonds
Non-Polar Covalent Bonds: chemical bonding defined as the equal sharing of electrons by two or more atoms to produce a shared attraction. The atoms tend to share electrons, so as to fill the outer electron shell, which can hold up to eight electrons (except for hydrogen and helium, which can accommodate only 2 electrons in the outer shell).
Atoms and Bonding - Covalent Bonds
How Covalent Bonds Form
An oxygen molecule contains one double bond, while a carbon dioxide molecule has two double bonds. A nitrogen molecule contains one triple bond.
Atoms and Bonding - Covalent Bonds
Unequal Sharing of Electrons
Fluorine forms a nonpolar bond with another fluorine atom. In hydrogen fluoride, fluorine attracts electrons more strongly than hydrogen does, so the bond formed is polar.
Atoms and Bonding - Covalent Bonds
Unequal Sharing of Electrons
A carbon dioxide molecule is a nonpolar molecule because of its straight-line shape. In contrast, a water molecule is a polar molecule because of its bent shape.
Atoms and Bonding - Bonding in Metals
Metallic Bonding
A metal crystal consists of positively charged metal ions embedded in a “sea” of valence electrons.