• Chapter 6: Chemistry of Life • Section 6.1 Atoms and Their Interactions

Elements

whether gold is a nugget or dust, it is still gold• Natural Elements in Living Things– Only 25 elements are essential to living organisms– There are 4 elements that make up 96% of human

mass. – Carbon, Hydrogen, Oxygen, Nitrogen (CHON)

Elements: – Substance that can’t be broken down into simpler

chemical substances. – (you should have this defined already!)

Trace Elements

• Trace Elements – Elements found in our body in small amounts. These are obtained by plants through the roots and in the food an animal eats.– Ex: Iron (Fe), Calcium (Ca), Phosphorous (P)– ^ 1-2 Letters ^ Symbols ^

Some Elements ThatMake Up the Human Body

Element SymbolPercent By Mass in Human Body

Element SymbolPercent By Mass in Human Body

Molybdenum

OxygenCarbonHydrogenNitrogenCalciumPhosphorusPotassiumSulfurSodiumChlorineMagnesium

Selenium

IronZincCopperIodineManganeseBoronChromium

Cobalt

Fluorine

OCHNCaPKSNaClMg

65.018.59.53.31.51.00.40.30.20.20.1

FeZnCuIMnBCrMoCoSeF

tracetracetracetracetracetracetracetracetracetracetrace

Atoms: Building Blocks of Elements

• Atom: Smallest particle of an element – (that maintains characteristics of that element)– The way these are structured affects their

properties and their chemical behaviorFound in rocks, plants, mammals, water, etc.

The Structure of an Atom

• Nucleus – the center of an atom– Protons – positively charged particle (p+)– Neutrons – neutral charged particle (n0)– Positively charged because of the protonsProtons define the distinct characteristics and

element will have.Ex. Iron (Fe) will have different characteristics and

proton # than Aluminum (Al)

Drawing Atoms/Electron Levels

• Draw/Label the following in the space provided

Neutron (No Charge)

Proton (pos+ Charge)

Electron Energy levels Electron (neg- Charge)

Nucleus

The Structure of an atom

Nucleus

Electron energy levels

The region of space surrounding the nucleus contains extremely small, negatively charged particles called electrons (e-)

This region of space is referred to as an electron cloud.

Electron energy levelsElectrons exist around

the nucleus in regions known as energy levels.

The 1st energy level can hold only two electrons. The 2nd level can hold a maximum of eight

electrons. The 3rd level can hold up to 18 electrons.

Overall, the atom has no net charge, opposites attract! Negative Electrons, Positive Nucleus/Protons

Nucleus8 protons (p+)8 neutrons (n0)

Oxygen atom

Orbitals/Energy Levels

electron

neutron

proton

2nd Energy levelHolds up to 8 electrons

1st Energy LevelHolds up to only 2 Electrons

Nucleus with Positive ++++ Charge!

Because opposites attract, the negatively charged electrons are held in the electron cloud by the positively charged nucleus.

Atoms of the same element always have the same number of protons but may contain

different numbers of neutrons.

Isotopes of an Element

Atoms of the same element that have different numbers of neutrons are called isotopes (I suh tophs) of that element.

Example: Carbon-14 – unstable, radiation caused to break apart. An Isotope of Cobalt for use against rapid growing cancer cells

A compound is a substance that is composed of atoms of two or more different elements that are chemically combined.

Compounds and Bonding

Table salt (NaCl) is a compound composed of the elements sodium (Na) and chlorine (Cl).

Atoms combine with other atoms only when the resulting compound is more stable than the individual atoms.

How covalent bonds form

For many elements, an atom becomes stable when its outermost energy level is full.

Sharing electrons (forming covalent bonds) with other atoms is one way for elements to become stable.

Two hydrogen atoms can combine with each other by sharing their

electrons.

How covalent bonds form

Each atom becomes stable by sharing its electron with the other atom.

Hydrogen molecule

How covalent bonds form

Click image to view movie.

How covalent bonds formThe attraction of the positively charged nuclei for the shared, negatively charged electrons holds the atoms together.

Opposites Attract!!

Hydrogen molecule

A covalent bond holds the two

hydrogen atoms together.

How covalent bonds form

A molecule is a group of atoms held together by covalent bonds. It has no overall charge.

Water molecule

An atom (or group of atoms) that gains or loses electrons has an electrical charge and is called an ion. An ion is a charged particle made of atoms.

How ionic bonds form

Ionic Bond: The attractive force between two ions of opposite charge.

Stand up, Stretch out, Mini Video!

• For this next activity, I will show the video TWICE, make sure you are paying attention.

• Use your powerpoint notes to DRAW– Element Na (Sodium) – Element Cl (Chlorine)– What must occur to create a charged ion

Chemical Reactions

Chemical reactions occur when bonds are formed or broken, causing substances to recombine into different substances.

Chemical Reactions

All of the chemical reactions that occur within an organism are referred to as that organism’s metabolism.

In a chemical reaction, substances that undergo chemical reactions, are called

reactants.

Writing chemical equations

Substances formed by chemical reactions,

are called products.

A molecule of table sugar can be represented by the formula: C12H22O11.

Writing chemical equations

The easiest way to understand chemical equations is to know that atoms are neither created nor destroyed in chemical reactions. They are simply rearranged.

A mixture is a combination of substances in which the individual components retain their own properties.

Mixtures and Solutions

Neither component of the mixture changes.

A solution is a mixture in which one or more substances (solutes) are distributed evenly in another substance (solvent).

Mixtures and Solutions

Sugar molecules in a powdered drink mix

dissolve easily in water to form a solution.

Chemical reactions can occur only when conditions are right.

Acids and bases

A reaction may depend on:

- energy availability

- temperature

- concentration of a substance

- pH of the surrounding environment

The pH is a measure of how acidic or basic a solution is.

Acids and bases

A scale with values ranging from below 0 to above 14 is used to measure pH.

More acidic Neutral More basic

Substances with a pH below 7 are acidic. An acid is any substance that forms hydrogen ions (H+) in water.

Acids and bases

A solution is neutral if its pH equals seven.

More acidic Neutral More basic

Substances with a pH above 7 are basic. A base is any substance that forms hydroxide ions (OH-) in water.

Acids and bases

pH 11