Bellwork: Mon. Aug. 24, 2015

Chemistry in Life Notebook 2

The Chemistry of Life 2-1 The Nature of Matter

Chapter 2: Atom: smallest unit of matter So Very Small that… In Greek, atomos means “unable to be cut” So Very Small that… 1 million atoms would be only as wide as your pinkie! Thousand of atoms are in each cell.

Atoms have equal numbers of protons (+) and electrons (-) so……. The total or net charge of an atom = zero or neutral

made of subatomic particles Nucleus contains the Protons p+ = +1 Neutrons n= zero Outside the nucleus are: Electrons e- = -1

Protons and Neutrons Protons and neutrons have about the same mass. Protons (+) and neutrons carry no charge at all. Strong forces bind protons and neutrons in the nucleus, at the center of the atom.

Atoms are neutral So, can you take a p+ away and still have the same neutral element? No, if you change the number of protons, you change the atom Some atoms “like” to lose electrons

Electrons are negatively charged particles (–) with only 1/1840 the mass of a proton. Electrons are in constant motion in the space surrounding the nucleus. They are attracted to the positively charged nucleus but remain outside the nucleus because of the energy of their motion.

Electrons Because atoms have equal numbers of electrons and protons, their positive and negative charges balance out, and atoms themselves are electrically neutral. The carbon atom shown has 6 protons and 6 electrons.

C=carbon H=hydrogen O=oxygen Cl = Chlorine P=phosphorous Na=sodium K=potassium

Let’s take a look at the Carbon (C) atom:

Element More than 100 elements are known… pure substance that consists entirely of one type of atom. More than 100 elements are known… Only about 2 dozen are common in living organisms. Represented by 1or 2 letter symbols. C = carbon, H = hydrogen,Na =sodium, and Hg = mercury….

Can you change the number of neutrons (n)? Yes, you can change the number of n and still have the same element. These special atoms are called…

Isotopes are… Elements (atoms) that differ in the number of neutrons that they contain

Radioactive Isotopes Some isotopes are radioactive: their nuclei are unstable and break down at a constant rate over time. Although radiation can be dangerous, radioactive isotopes have a number of important scientific and practical uses. Geologists can determine the ages of rocks and fossils by analyzing the isotopes found in them.

Example Isotopes Carbon 12, Carbon 13 or Carbon 14 Each has 6p+, 6 e-, but they differ in the number of neutrons they have: Carbon 12 has 6n Carbon 13 has 7n Carbon 14 has 8n (it is radioactive!) (ever heard of Carbon-14 Dating?)

Molecules- 2 or more atoms bonded together Molecules- 2 or more atoms bonded together. Can be the same element or different elements.

chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions.

Chemical Compounds Two or more different types of elements added together 2 Hydrogen & 1 oxygen =water compound Properties of elements change when they make compounds Hydrogen = gas Oxygen = gas H2O =liquid

Chemical Bonds: hold two or more atoms together. 2 main types: Covalent bonds (e- shared) and Ionic bonds (e- transferred)

Chemical Formula shows composition of compounds. Water: H2O. H = 2 O = 1 a 2:1 ratio table salt: NaCl, Na = 1, Cl = 1 sodium and chlorine - a 1:1 ratio.

Ionic Bond: is formed when one or more electrons are transferred from one atom to another. ions: atoms that lose electrons or gain electrons. (An atom that loses electrons becomes positively charged. An atom that gains electrons has a negative charge. )

Ionic bond form when a metal and a nonmetal form a bond Metals lose an e- Nonmetals gain an e-

Ionic Bonds Ionic bonds form between sodium and chlorine to form NaCl, table salt.

Example: Cl=chlorine a poisonous gas!   Normally 17p+ & 17e- So, what is the charge on normal Cl? Neutral or zero Na=sodium a dangerous reactive metal   Normally 11p+ & 11e- So, what is the charge on normal Na? But…When Na+ and Cl- bond…… Sodium looses an e- Cl gains an e- from sodium What are their new charges? Na+ & Cl- = NaCl (sodium chloride) Do you know what this is? Table salt  

- Covalent Bond (Co- means “share” like cooperate) e- are shared between atoms in the bond and are called molecules  Example water (H2O)…. What others do you see in the diagram?

Carbon can form Single bond Double bond Triple bond (In macromolecules we will be studying) Carbon can form

Covalent Bonds When the atoms share two electrons, the bond is called a single covalent bond. Sometimes the atoms share four electrons and form a double bond. In a few cases, atoms can share six electrons, forming a triple bond.

Covalent Bonds When atoms of the same element join together, they also form a molecule. Oxygen molecules in the air you breathe consist of two oxygen atoms joined by covalent bonds.

Glucose: C6H12O6 What kind of bond is this? How many electrons are shared?

ethylene What type of bond? How many electrons are shared?

Acetylene Carbon monoxide What type of covalent bond is this Acetylene Carbon monoxide What type of covalent bond is this? How many electrons are shared?

Large Surface Area of Gecko Feet

Sooooooooo…. What happens??????? Atoms of different elements don’t have the same ability to attract electrons - some have a stronger attraction for electrons than do others. When the atoms in a covalent bond share electrons, the sharing is not always equal. Even when the sharing is equal, the rapid movement of electrons can create regions on a molecule that have a tiny positive or negative charge. Sooooooooo…. What happens???????

Van der Waals Forces Van der Waals forces a slight force of attraction between oppositely charged regions of molecules when they are close together Named after the scientist who discovered them. Although van der Waals forces are not as strong as ionic bonds or covalent bonds, they can hold molecules together, especially when the molecules are large.

Like: Geckos Feet! When two molecules come near each other they can attract each other… These are not bonds with in a compound, They are attractions called Van der Waals forces They are weaker Think about how a magnet is attracted to the fridge but not bonded to it Gecko’s are able to walk up the side of a tank because their feet have a weak Van der Waals attraction to the wall! They have lots of ridges on their feet so all those weakly attracted ridges have enough power to stick! http://www.youtube.com/watch?NR=1&v=NWH624jPW0w

Elements # next to the letter on the periodic chart tells you the number of protons and is called the Atomic Number Carbon (C) is number 6 so it has 6 protons AND if it is neutral it must have 6 electrons Any atom with 6 protons is carbon If it has a different number of p+ it’s no longer carbon

Finding Atomic weight – (MASS) e- (electrons) are so small we ignore them for mass We add up the p+ 6 and n 6 for mass Some Carbon has a mass of 12 To find the number of Neutrons subtract the mass (weight) from the number of protons 12 – 6p+ = 6n

8 8 8 About Oxygen… 1 6 - 8 atomic # = 8 atomic mass = 16 Atomic number always tells you the number of protons! 1 6 - 8 atomic # = 8 atomic mass = 16 So…how do you knw the number of e- = ____ p+ = ____ n = ____ 8 8 8

extra Describe the structure of atoms. Why do all isotopes of an element have the same chemical properties? How are isotopes of the same element different? What is a covalent bond? Ionic Bond? What is a compound, how is it related to a molecule? How do van der Waals forces hold molecules together? How are van der Waals forces different than ionic bonds?

OldBellwork: Friday Sept 2, 2011 drops on penny 1. __________________________ holds water on a penny. 2. ____________________ holds water to the penny. 3. ________________ holds water molecules to each other on the penny by _____________________ 4. bonding of slightly charges H molecules, because water is a __________________ molecule Use these terms: Polar Adhesion Cohesion Hydrogen Surface tension

Bellwork: Aug. 28, 2014 Of the 92 naturally occurring elements, living things are composed of only about 26, and 6 of those 26 make up practically all of the weight of most living things. The other 20 elements essential for life are present in very small amounts, some in such tiny amounts that they are designated simply as "trace elements". The six most abundant elements: What do you think? 1 2 3 4 5 6

The six most abundant elements: 1 2 3 4 5 6