The Basic Structure and Function of Atoms, Molecules and Chemical Bonds: Covalent, Ionic, and Hydrogen

1. The Basic Structure and Function of Atoms, Molecules and Chemical Bonds: Covalent, Ionic, and Hydrogen

2. Atoms Are the Units of Structure and Function of Matter • Atoms are composed of : • Protons – have mass, are positively charged, reside in the nucleus and give the specific characteristics to an atom. • Neutrons – have mass are neutral and reside in the nucleus. • Electrons – have very little mass, are negatively charged and reside in energy levels that orbit the nucleus.

3. Atomic Statistics • Chemical symbols for an element shows its mass (weight) number at the top and its atomic number at the bottom. This is the symbol for carbon. A neutral Carbon atoms has six protons, six electrons, and 12 - 6 = 6 neutrons. • Atomic Number – the # of protons in an atom’s nucleus, this determines the “kind” of atom. In neutral atoms, the # of protons is equal to the # of electrons. Elements are composed of only one kind of atom. • Ions – Atoms that have different # of protons versus electrons, therefore they are “charged”. • Atomic Mass – the # of protons plus the number of neutrons in an atom’s nucleus. Aka atomic weight. • Isotopes – atoms that have the same # of protons but vary in the number of neutrons.

4. Atoms: Components of Elements • Atoms of the same kind have the same number of protons. • Elements are substances that cannot be broken down by ordinary chemical means. They are composed of only one kind of atom. • Click on the link below for the Periodic Table of Elements http://images.google.com/imgres?imgurl=http://www.dayah.com/periodic/Images/periodic%2520table.png&imgrefurl=http://www.dayah.com/periodic/&h=1480&w=2084&sz=91&hl=en&start=1&tbnid=0VVvXVkQCVztRM:&tbnh=106&tbnw=150&prev=/images%3Fq%3Dperiodic%2Btable%2Bof%2

5. Elements Essential to Life • Carbon, Hydrogen, Oxygen, and Nitrogen are the four elements that make up most of the matter in living things. • In the body of organisms, most other essential elements are found only in trace amounts.

6. Carbon Is the Structural Backbone of Organic Molecules • Organic chemistry pertains to Carbon based molecules found in living things. • Carbon can chemically bond to four other atoms and serves as a “structural” backbone for organic molecules.

7. Electron Arrangement in an Atom’s Outermost Energy Level Determines Chemical Bonding Properties • In an atom, electrons reside at certain energy levels, which are at specific distances away from the nucleus, known as shells. • The first shell, closest to the nucleus, may “fit” up to two electrons, a duet. • Outer shells, may fit up to eight electrons, an octet. • Atoms, whose outermost energy levels are not full, participate in chemical bonding with other atoms.

8. Ionic Bonding • Ionic bonding occurs when one atom gives its electron to another. • Ions, are formed as the atom that gains the electron becomes negatively charged and the atom that loses the electron becomes positively charged. • Ionic bonds form due to the attraction between ions of opposite charge.

9. Covalent Bonds • Covalent bonds occur when atoms share one or more pairs of outer shell electrons with each other to fulfill their duet and/or octet. • Single bond – one pair of electrons is shared. • Double bond - two pairs of electrons are shared. • Triple bond – three pairs of electrons are shared.

10. Polar Covalent Bonds When electrons are not equally shared between two atoms, that are chemically combined in a covalent bond, one atom will pick up an overall negative charge and the other atom will pick up an overall positive charge. This produces polar compounds, such as water, H2O.

11. Hydrogen Bonds • Hydrogen bonds are weak electrostatic bonds that are formed when Hydrogen is a part of a polar covalent bond, where its partial positive charge will allow it to share attraction with other electronegative atoms, such as Oxygen. • Ex. Water H2O

12. The Hierarchy of Molecular Complexity Leads to Chemical Structures that Have Specific Functions