Chemistry Concepts What is matter? What are some phases of matter? What are some properties of matter? What does an atom look like? How do you use the periodic table to predict element behavior? What are chemical reactions?

Matter Matter is anything that has mass and takes up space. Examples? Non-examples? All matter has properties or characteristics…

Properties of Matter Physical Properties Can be observed without changing the matter’s chemical composition. Examples: Temperature Length Mass Physical State (gas, liquid, solid)

Properties of Matter Chemical Properties Observed when matter changes into a new substance Examples Reactivity Flammability

The Atom An atom is the smallest building block of matter. Atoms are made of neutrons, protons and electrons. The nucleus of an atom is extremely small in comparison to the atom. It contains the neutrons and protons.

Atomic Particles proton neutron electron Found in a nucleus with a positive charge. Number of these gives atomic number. neutron Found in the nucleus of an atom. It is almost identical in mass to a proton, but carries no electric charge. electron Found in the electron cloud surrounding the nucleus. This particle has a negative charge.

Atomic Energy Levels The regions where electrons move are called energy levels because the electrons in the different regions have different amounts of energy. Energy levels Nucleus with protons & neutrons

Energy Levels cont… Each energy level can hold a fixed number of electrons. The 1st energy level can hold 2 e- The higher energy levels can hold up to 18 e- (usually 8e-) An atom with its outer energy levels filled with electrons are more stable than ones without their outer levels filled.

Atoms & Elements An element is a substance that cannot be broken down into a simpler substance by chemical means. An element is made up of only one type of atom. Atoms of different elements can bond together for form compounds. When elements bond together their chemical properties change.

Characteristics of Elements Each element has different Atomic Number – number of protons Mass Number – number of protons plus the number of neutrons Physical Properties Chemical Properties

Brief History of the Periodic Table German Lothar Meyer created a table that was an accurate (for the time) accounting of the known facts about each element, such as melting point and atomic volume. The table clearly showed the existence of periodic chemical families. In 1870 Meyer's table and description of the periodic law was published.

History continued… A year earlier however, the 35 year old Mendeleev presented a much bolder and scientifically useful table. In it, the periodic relationship between chemical groups, that is, elements with a similar characteristics of reaction, is clearly illustrated. In a scientific triumph, gaps in the table accurately predicted undiscovered elements.

Mendeleev’s Table Although it is nearly 130 years old, Mendeleev's table differs little from the charts on the walls of laboratories today. The insight obtained in that productive decade resulted in a tool that furthers understanding and eases the use of chemistry in every laboratory in the world.

Periodic Table of Elements The periodic table is organized like a big grid. If you have ever looked at a grid, you know that there are rows (left to right) and columns (up and down). The periodic table has rows and columns too, and they each mean something different. The elements are placed in specific places because of the way they look and act. The Periodic table is designed to help you predict what an element's physical and chemical properties are. You can also predict what elements will bond with each other.

Organization of the Periodic Table When you look at the picture to the right, you can see that the rows are different colors. Even though they skip some squares in between, all of the rows go left to right. When you look at a periodic table, each of the rows are considered to be different PERIODS (Get it? Like PERIODic table)

Organization cont… In the periodic table, elements have something in common if they are in the same row. All of the elements in a period have the same number of atomic energy levels. Every element in the top row (the first period) has one level for its electrons. All of the elements in the second row (the second period) have two level for their electrons. It goes down the periodic table like that. At this time, the maximum number of levels is seven. Elements in a period are not alike in chemical or physical properties.

Organization cont… The columns in the Periodic Table are called GROUPS. You can know properties of a certain element by knowing which group it belongs to. The elements in a group have the same number of electrons in their outer shell.

Organization cont… Every element in the first column (group one) has one electron is its outer shell. Every element on the second column (group two) has two electrons in the outer shell. As you keep counting the columns and you'll know how many electrons are in the outer shell. The elements in between, with the grey color, are called TRANSITION elements. They have special electron rules.

Reading the Periodic Table When you look at the periodic table, you should notice that each box represents a different element, and each box contains vital information about the element .

Think inside the Box The top number is the atomic number. The atomic number tells how many protons are in one atom of that element. Since no two elements have the same atomic number, no two elements have the same number of protons. 6 C Carbon 12.011

Thinking cont… C Carbon 12.011 The large letter is the element's symbol, and just below that is the element's name. Each element has its own unique symbol and name. Below the name is the element's atomic mass. The atomic mass is the number of protons plus the number of neutrons. 6 C Carbon 12.011

Chemical Reactions Let's start with the idea of a reaction. In chemistry, a reaction is when two or more molecules interact and something happens. That's it. What molecules are they? How do they interact? What happens? Those are all the possibilities in reactions. The possibilities are infinite.

KEY POINT #1 A chemical change must occur. You start with one compound and turn it into another. That's an example of a chemical change. A steel garbage can rusting. That rusting happens because the iron in the metal combines with oxygen in the atmosphere. A refrigerator or air conditioner cooling air is not a reaction... That is a physical change.

KEY POINT #2 It could be ions, molecules or pure atoms. We said molecules in the above section, but a reaction can happen with anything, just as long as a chemical change occurs (not a physical one).

KEY POINT #3 Single reactions often happen as part of a larger series of reactions. Take something as simple as the leaves changing color in the fall. A whole series of reactions (hundreds actually) are needed to make it happen.

Bonding When atoms combine, it is called bonding. There are two types of bonds Ionic Covalent

Ionic Bonds Sometimes, atoms will become more stable if they either gain or lose electrons. For example, the element chlorine becomes more stable when it gains an electron, and sodium becomes more stable when it loses an electron. If an atom of chlorine and an atom of sodium come near enough to one another, an electron from the sodium can actually jump to the chlorine atom. However, the sodium atom now has more protons than electrons, so it has a positive charge. The chlorine atom now has an additional electron and so has a negative charge. These charged atoms are called ions. Ions of opposite charges, like the sodium and chlorine ions, are attracted to one another in what is called an ionic bond.

Covalent Bonds In other cases, two atoms will share the electrons so that each becomes more stable. For example, oxygen, which normally has eight electrons, happens to become more stable when it has two additional electrons. If two oxygen atoms come together, they can each contribute a pair of electrons to be shared by both atoms. This type of sharing is called a covalent bond. In the case of the oxygen atoms, the electrons are shared exactly equally. However, in most cases, one atom pulls on the electrons more than the other. In these bonds, one side of the molecule is slightly more negative since the negatively charged electrons are closer to that side. These molecules are said to be polar (water is an example), whereas molecules which share the electrons equally are nonpolar.

Questions to Ponder… What is matter and what are some of its properties? What are the differences between physical and chemical properties? What are the 3 atomic particles, where are they located and what are their charges and masses? What information about elements is in the periodic table? How can the arrangement of the periodic table help you make predictions about the chemical and physical properties of elements? Describe chemical reactions. Compare/Contrast ionic & covalent bonds.