Chapter 5 Notes (to section 5.5)1Matter - is anything that has mass and takes up space. So chemistry is the study of almost everything

Substance - a particular kind of matter that has a uniform and definite composition. (i.e. Sugar is a substance whereas soda is not)

- matter can exist in three different states: solid, liquid, and gas(Be able to define and describe 3 states)

Properties of Matter- all samples of substances have identical properties/ distinguishing features

- Mixtures consist of a physical blend of two or more substances. A mixture has variable composition and may be classified as homogeneous or heterogeneous.

heteros = different, genos = kind, homo = same ✓ Be able to compare and contrast homogeneous/heterogeneous mixturesHomogeneous * Parts of the mixture are evenly distributed.* Aka solutions (solute is dissolved in solvent) Examples:  Sugar (solute) and Water (solvent) Salt (solute) and Water (solvent)Heterogeneous * Parts of the mixture are not evenly distributed.* Aka a mechanical mixture Examples: - Salt and Pepper - Oil and Water - Unshaken salad dressing

By separating mixtures into their components we break them into their purest forms....... elements and compounds

Element a substance composed of only one type of atom. They can not be broken down into simpler form. They are the building blocks of all other substances.

Carbon only has carbon atoms, sulfur only has sulfur atoms

Compound a chemical substance composed of 2 or more atoms in definite ratios. It can be broken down into its simplest parts by a chemical reaction.

CO2 is a gas composed of carbon and oxygen; for every 1 carbon atom there are 2 oxygen atoms

* the chemical and physical properties of compounds are quite different from those of their component elements. (Ex: sugar/ table salt)

Physical Properties Chemical Propertiescolor How a substance reacts: boiling point Corrosive (reacts with metal);freezing point flammable (reacts with fire);mass caustic (reacts with skin);density reacts violently with air or watertexture

1physical change VS. chemical change- physical changes are - chemical changes are not easily reversible reversed- doesn’t require heat - generally requires heat - change in state - change in composition- mass and energy conserved - mass and energy conserved - key words: cutting, grinding - key words: rot, rust, decompose bending grow, decay, sprout

- Physical changes of a substance will alter the substance without changing its composition. (Cutting, grinding, melting, freezing). A chemical change, however, will alter the substances’ identity

ElementsEvery element is represented by a chemical symbol. The chemical symbols are a kind of scientific alphabet. Chemical symbols are used to write chemical formulas which tells us the elements and the proportions of each.

Example 1.The chemical symbol for Hydrogen is H; while the chemical symbol for Gold is Au.

Example 2. The chemical symbol for sugar (glucose) is C6 H12 O6. This means that each molecule of glucose has 6 C-atoms, 12 H-atoms, and 6 O-atoms.

1The Periodic Table-Dmitri Mendeleev (1834-1907) sequenced the elements in increasing atomic mass. Because Mendeleev’s arrangement

highlighted periodic (repeating) patterns of properties, it was called a periodic table. - The modern periodic table organizes the elements according to atomic number.

Combinations of these elements make compounds An elements position on the periodic table is characteristic of the element Metals are found on the left-hand side of the table Non-metals are found on the right-hand side of the periodic table

Be able to compare metals and non-metals (see page 185 in your text).

- The table is organized in rows and columns according to similarities in their properties. - Elements are arranged in 7 numbered periods (horizontal rows) and 18 numbered groups (vertical columns).

Know terms:Representative elements - Metals (high luster when clean, high electrical conductivity, are ductile, are malleable)Transition metalsInner transition metalsNonmetals(nonlustrous, poor conductors of electricity,

Semimetals or metalloids(elements with the properties of both metals and nonmetals)

alkali metals (Group 1)alkaline earth metals (Group 2)halogens (Group 17 or 7 in some texts)noble gases (Group 18 or 8 in some texts)

Elements and Atomic Structure• Atoms are the basis of chemistry and the basis of everything in the universe. Remember all matter is composed of

atoms!• Atom – smallest particle of an element that still retains the properties of that element• the atom is a microscopic structure. It is similar to the cell in biology. Like the cell the atom can be broken down

into it simplest parts as well.

• Atoms can be broken down into electrons, protons, and neutrons. Electrons are negatively charged subatomic particles. Symbol is e- . (J.J. Thompson) Protons are positively charged subatomic particles. (Rutherford)Neutrons are subatomic particles with no charge. (James Chadwick)

• The proton & neutron are found in the center of the atom, a place called the nucleus.• The electrons orbit the nucleus.

Protons• Protons are very important because they help determine the identity of an element• They are inside the nucleus• They have a positive charge +• Atom Identity – the number of protons an atom has will determine its identity.

Neutrons• Found inside the nucleus• Have a neutral charge• Have a relative mass of 1 atomic unit• Important for creating isotopes (coming soon!)

Electrons• Found outside the nucleus• Forms an orbital cloud (the location where an electron might be found)• Has a negative charge –

Different elements have different numbers of subatomic particles thus giving different elements different characteristics/properties

• So how do we know how many subatomic particles an element has?

Every element on the table has an atomic number. The atomic number is the number of protons and it is also the number of electrons in an atom of an element. Every element has a mass number (neutral elements) which is formed by adding the number of protons and neutrons – as a result the mass of an element comes from the nucleus (where the protons and neutrons are located).

# of protons = atomic number# of neutrons = mass number - atomic number# of electrons = number of protons (When the atom is neutral)

Neils Bohr (1913) – • Electrons move around the nucleus in paths called orbitals • Each electron in an orbit has a definite amount of energy ; further away from nucleus = greater energy• Electrons cannot exist between orbits, but they can move up or down from one orbit to another• Electrons are more stable when they are at lower energy (closer to the nucleus)

1Bohr-Rutherford diagrams are a common way to show the arrangement of electrons in an atom. Circles are drawn around the atomic symbol; each circle represents an energy level; the dots represent electrons that occupy each energy level.

The first ring can contain a maximum of 2 electrons, the second energy level a max of 8 electrons. The third has a maximum of 18 electrons but for now, only has 8 electrons.

The outer shell of an atom is called the valence shell and the electrons in this shell are called valence electrons. They will be important as these electrons are the ones responsible for reactivity, bonding etc.

Atoms by themselves are neutral (have no charge). The number of protons and electrons are balanced or equal. What happens if an atom loses or gains an electron? It becomes an ION. Ion – charged atom in which the number of electrons is different from the number of protons due to a loss or gain

of electrons Positive ions are called cations Negative ions are called anions

Ionic Charge – numerical value of the electric charge with a + or –. Formed by the difference between the number of protons and electrons

Examples: Al3+, F1-,S2-

Note: When nonmetals gain electrons to form ions the name of the ion changes its ending to “ide” (E.g. F- ion is called a fluoride ion)

Examples:1. Ca is a calcium atom. Ca2+ is a CALCIUM ion (cation). It LOST 2 electrons. The ending of the name stays the same with cations!2. I is an iodine atom. I1- is an iodide ion (anion). Iodine gained 1 ELECTRON. The ending changes with anions!