2. Atoms and Bonding Table of Contents
Atoms, Bonding, and the Periodic Table
Ionic Bonds
Covalent Bonds
Bonding in Metals

3. Elements
Element- A pure substance that cannot be broken down into any other substances by ordinary chemical or physical means
Elements are pure substances, composed of only one type of atom
Can be identified by specific chemical and physical properties
92 elements occur naturally, the rest have been synthetically created in labs
Elements are often called the building blocks of matter because all matter is composed of one element or a combination of two or more elements

4. Atoms
Atoms- The smallest part of an element that has all the properties of that element
The basic particle from which all elements are made
The building blocks of matter
Made up of three main types of particles:
Protons- Positively charged
particles located in the nucleus
Neutrons- Particles with no
charge (neutral) found in the nucleus
Electrons- Negatively charged
particles that whirl around in a cloudlike
region beyond the nucleus of the atom

5. Molecules
Atoms of elements can chemically combine to form larger particles called molecules
Molecule- A combination of two or more atoms held together by chemical bonds
Represented by chemical formulas (ex.- water H2O)
Can be made of two or more of the same kind of atoms (ex.- atmospheric oxygen O2)
Can be made of different types of atoms (ex.- water H2O)

6. Compounds
Compound- substance made of atoms of different elements that are chemically combined in a set ratio (ex.- table salt NaCl)
When elements are chemically combined, they form compounds having properties that are different from those of the uncombined elements
A compound may be represented by a chemical formula, which shows the elements in the compound and the ratio of the atoms
When atoms combine, only the electrons in the
outermost energy shells combine
This combining of elements to form new
substances is called chemical bonding

7. Mixtures
Mixture- Matter that is made of two or more substances- elements, compounds, or both- that are together in the same place but are not chemically combined
Mixtures differ from compounds in two ways:
Each substance in a mixture keeps its individual properties
The parts of a mixture are not combined in a set ratio
Components can be separated out by normal physical means

8. The Periodic Table
Periodic Table- A table in which the elements are arranged in order of increasing atomic number
The table has one square for each element
Each square lists the element’s name, chemical symbol, atomic number, and average atomic mass
Periodic Vocabulary:
Chemical Symbol- A one or two letter representation of an element
Atomic number- The number of protons in the nucleus of an atom
Average Atomic mass- The average mass of an atom for a particular element, based upon the number of protons and neutrons in the nucleus of an atom (based upon the combined percentages of all its isotopes)

9. Organizing the Periodic Table
Properties of an element can be predicted from its location in the periodic table
Elements are placed in horizontal rows (called periods) based on atomic number
Atomic number increases across a period
Both the number of protons and the number of electrons increases by one as you move from one element to the next
Elements are placed in vertical columns (called groups or families) based on having the same number of electrons in their outermost energy shell which gives them similar chemical properties

10. Atoms, Bonding, and the Periodic Table
Electron Dot Diagrams
The valence electrons of
an atom are shown as dots around the symbol of the element. Complete the electron dot diagram for neon.
Valence electrons
Electrons at higher energy levels that are involved in chemical bonding

11. Atoms, Bonding, and the Periodic Table1 8
Periodic Table of the Elements
The periodic table is arranged in order of increasing atomic number. The number of valence electrons also increases from left to right across a period. What is the number of valence electrons for each group? 4 2

12. Atoms, Bonding, and the Periodic Table
The symbols for the elements in Periods 2 and 3 are shown below. Complete the electron dot diagrams for nitrogen, oxygen, fluorine, sodium, magnesium, aluminum, silicon, and argon.

13. Atoms, Bonding, and the Periodic Table
Groups of Elements 1
High 7
High 8
Low

14. Ionic Bonds How Ions Form
An atom that loses one of its electrons becomes a positively charged ion. The atom that gains the electron becomes a negatively charged ion.

15. Ionic Bonds
Ions
The table lists the names of some common ions, their charges, and their symbols.

16. Ionic Bonds Formation of an Ionic Bond
Follow the steps to see how an ionic bond forms between a sodium atom and a chlorine atom. Complete the electron dot diagrams.

17. Ionic Bonds
Halite
Ions in ionic compounds are arranged in three-dimensional shapes called crystals. Some have a cubic shape.

18. Ionic Bonds
Galena
Galena, or lead sulfide (PbS), has a structure similar to that of table salt.

19. Covalent Bonds Sharing Electrons
By sharing 2 electrons in a covalent bond, each fluorine atom gains a stable set of 8 valence electrons. Which are the shared electrons that form a covalent bond between the
2 fluorine atoms?

20. Covalent Bonds Covalent Bonds
Atoms can form single, double, and triple covalent bonds by sharing one or more pairs of electrons.

21. Covalent Bonds Nonpolar and Polar Bonds
Hydrogen forms a nonpolar bond with another hydrogen atom. In hydrogen fluoride, fluorine attracts electrons more strongly than hydrogen does. The bond formed is polar.

22. Covalent Bonds Nonpolar and Polar Molecules
Both carbon dioxide and water molecules contain polar bonds. Where would + and - signs be placed to show positive and negative charges?

23. Covalent Bonds
Bonding Determines the Properties of a Substance
Complete the information, using water and sodium chloride as examples.
Water forms when two nonmetals (hydrogen and oxygen) share electrons
Sodium chloride forms when positive and negative ions attract one another
And when combined, the two make a mixture commonly known as saltwater

24. Bonding in Metals Metallic Bonding
The positively charged metal ions are embedded in a “sea” of valence electrons.

25. Properties of Metals
The unique properties of metals result from the ability of their valence electrons to move about freely
Properties of metals include:
Luster- the way light reflects off the surface
Malleability- can be rolled into thin sheets
Ductility - can be bent easily
Thermal Conductivity- conduct heat easily
Electrical Conductivity- conduct electric current easily