The Chemistry of Living Things. An introduction to atoms, elements, compounds and mixtures.

What do you remember about atoms? Do you remember what the building blocks of atoms are? How is the atom of one element different from another? How do we organize all of the different elements?

Beyond cellular biology We learned about the building blocks of life, the cell, earlier in the year. In our last unit we saw how cells joined together to form large and complex organisms. Now we will learn about the building blocks of cells as well as all matter in the universe. Atoms are the basic building blocks of all matter.

What’s the matter? Matter can be defined as anything that has mass and takes up space. On earth, the three phases of matter are solids, liquids and gases. In stars there exists a fourth phase of matter called plasma. Plasma is super-heated ionized gas which exists on earth only as lightning.*

Plasma on Earth In addition to lightning there are also plasma lasers and the northern lights. Even neon lights are an example of plasma.

The Atom Atoms are made up of 3 subatomic particles found within the two regions of the cell. The particles are protons, neutrons and electrons. Protons and neutrons are found inside the nucleus of the atom, and electrons are found in the area surrounding the nucleus.

Image of Atom

Subatomic particles The subatomic particles have two very important characteristics that we must memorize, and that is mass and charge. Subatomic particle Mass Charge Proton 1 +1 Neutron Electron -1

The nucleus The nucleus of the atom contains all of the protons and neutrons. It makes up virtually all of the mass of the atom and has a net positive charge. The nucleus of an atom is much, much, smaller than the nucleus of a cell. Relative scale of cell and atom

The electrons The electrons orbit the nucleus in distinct energy levels or shells. The first energy level, which is closest to the nucleus, can contain a maximum of 2 electrons before it is filled. Each energy level after that if further away from the nucleus and can contain up to 8 electrons.*

Electron energy levels

Elements Atoms differ in the number of protons, neutrons and electrons they possess. The number of protons in the nucleus is referred to as it’s atomic number. An element refers to all atoms that have the same atomic number. Eg. All atoms of the element carbon have 6 protons in their nucleus.

The Periodic table. All the known elements are arranged in order of increasing atomic number on the periodic table of elements.

Atomic Symbols. All of the elements are referred to by a symbol. The symbol consists of either one or two letters. For symbols using one letter, it is capitalized. (eg. Carbon = C) For symbols using to letters, the first letter is capitalized and the second is not. (eg. Chlorine = Cl)

The important elements of life. All life on earth is made up mostly of just four elements. Carbon ( C ), Oxygen ( O ), Hydrogen ( H ) and Nitrogen ( N ). The next two most common elements are Sulfur ( S ) and Phosphorous ( P ) and are found in much lower amounts.

Special musical guests..they might be giants. The elements

Mass number. Atomic number refers to the number of protons in the nucleus of an atom. Mass number refers to the number of protons plus the number of neutrons found in the nucleus of an atom. If you subtract atomic # from mass # you get the number of neutrons. Atomic # Mass #

Pure substances. An atom is the smallest unit of an element that still possesses the properties of that element. Because of this, elements are considered to be pure substances. Every atom of gold is identical to every other atom of gold in the universe. Compounds are also considered to be pure substances.

Compounds. a substance formed by the chemical union of two or more elements or ingredients in definite proportion by weight. An example would be water. Each molecule of water contains two atoms of hydrogen and one atom of oxygen. (H2O) Every molecule of water is identical to every other molecule of water in the universe.

What is a molecule? A group of two or more atoms linked together by sharing electrons in a chemical bond. The atoms can be different as in the case of water. (We have two H and one O). The atoms can be of the same element, as is the case of the gas ozone (O3). The atoms in a compound can only be separated by chemical means.

Mixtures. Mixtures are composed of one or more substances that are not chemically combined, and can be separated. Salt dissolved in water and chocolate chip cookies are examples of mixtures. Mixtures are not pure substances since the ratio of the substances which make them up are not always identical to each other. All the chocolate chip cookies in the world do not have the same number of chips as every other one. A composition of two or more substances that are not chemically combined with each other and are capable of being separated. or more substances that are not chemically combined with each other and are capable of being separated.