1. Chemical Bonds

2. Elements, Atoms, and Ions
Chemistry I: Chapter 2b
Chemistry I Honors: Chapter 3
ICP: Chapter 17

3. The Language of Chemistry
CHEMICAL ELEMENTS -
pure substances that cannot be decomposed by ordinary means to other substances.
Aluminum
Bromine
Sodium

4. The Language of Chemistry
The elements, their names, and symbols are given on the PERIODIC TABLE
How many elements are there?

5. The Periodic Table
Dmitri Mendeleev ( )

6. The Atom nucleus (of protons and neutrons)
An atom consists of a
nucleus
(of protons and neutrons)
electrons in space about the nucleus.
Electron cloud
Nucleus

7. A MOLECULE is the smallest unit of a compound that retains the chemical characteristics of the compound.
Composition of molecules is given by a MOLECULAR FORMULA
H2O
C8H10N4O2 - caffeine

8. Copper atoms on silica surface.
An __Atom___ is the smallest particle of an element that has the chemical properties of the element.
Copper atoms on silica surface.
Distance across = 1.8 nanometer (1.8 x 10-9 m)

9. CHEMICAL COMPOUNDS are composed of atoms and so can be decomposed to those atoms.
The red compound is composed of • nickel (Ni) (silver) • carbon (C) (black) • hydrogen (H) (white) • oxygen (O) (red) • nitrogen (N) (blue)

10. Compounds composed of 2 or more elements in a fixed ratio
properties differ from those of individual elements
EX: table salt (NaCl)

11. ATOMIC COMPOSITION Protons (p+) Electrons (e-) Neutrons (no)
+ electrical charge
mass = x g
relative mass = atomic mass units (amu) but we can round to 1
Electrons (e-)
negative electrical charge
relative mass = amu but we can round to 0
Neutrons (no)
no electrical charge
mass = amu but we can round to 1

12. IONS
IONS are atoms or groups of atoms with a positive or negative charge.
Taking away an electron from an atom gives a CATION with a positive charge
Adding an electron to an atom gives an ANION with a negative charge.
To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na+ Ca+2 I- O-2
Na Ca I O

13. IONIC BOND bond formed between two ions by the transfer of electrons

14. Ionic Bonds: One Big Greedy Thief Dog!

15. 1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

16. COVALENT BOND bond formed by the sharing of electrons

17. Covalent Bond
Between nonmetallic elements of similar electronegativity.
Formed by sharing electron pairs
Stable non-ionizing particles, they are not conductors at any state
Examples; O2, CO2, C2H6, H2O, SiC

18. Covalent Bonds

19. when electrons are shared equally
NONPOLAR COVALENT BONDS
when electrons are shared equally
H2 or Cl2

20. 2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons.
Oxygen Atom
Oxygen Atom
Oxygen Molecule (O2)

21. when electrons are shared but shared unequally
POLAR COVALENT BONDS
when electrons are shared but shared unequally
H2O

22. Polar Covalent Bonds: Unevenly matched, but willing to share.

23. - water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.