Science benchmark

Proton charge and location

Positive (+) charge and located in the nucleus of an atom.

Neutron charge and location

Neutral (0) charge and located in the nucleus of an atom.

Electron charge and location

Negative (-) charge and located outside the nucleus in the electron cloud.

Atomic number definition

The number of protons in an atom which determines the element.

Nucleus location and composition

Located in the center of an atom, has a positive charge, and is made of protons and neutrons.

Valence electrons purpose

Determines the properties of an atom and are located in the outermost energy level of electrons.

Common property of all periodic table elements

All are pure substances, each element has the same type of atoms.

Most metallic elements location

Groups 1 & 2; left side of the periodic table, they are good conductors and shiny.

Least metallic elements location

Groups 17 & 18 nonmetals; right side of the periodic table, poor conductors and dull.

Group 1 name and properties

Alkali metals; the most reactive metals with 1 valence electron.

staircase line purpose on the periodic table

Indicates the location of metalloids between metals and nonmetals on the periodic table.

Group 2 name and properties

Alkaline-earth metals; less reactive than group 1, have 2 valence electrons.

Group 3-12 name

Transition metals located in the middle of the periodic table.

Group 17 name and properties

Halogens; the most reactive nonmetals with 7 valence electrons.

Group 18 name and properties

Noble gases; the least reactive of elements with a full valence electron level.

Group number purpose

Indicates the number of valence electrons in atoms within the column, excluding transition metals.

Exception to group number rule

Helium, a noble gas in group 18, which only has 2 valence electrons.

Chemical change of reactants

Bonds of reactants break and reform for new products with different properties.

Signs of chemical change

Include color change, heat/light/sound production, gas bubbles formed, and foam produced.

Law of conservation of mass/matter

Mass/matter cannot be created nor destroyed; it only changes forms.

Atoms in a chemical reaction must

The number of reactants atoms must equal the number of products atoms; everything must be the same.

Ionic compound formation

Formed by a metal and a nonmetal; valence electrons are transferred, example NaCl, neutral.

Cation charge and formation

Positive ion made by metals that always lose valence electrons.

Anion charge and formation

Negative ion made by nonmetals that always gain valence electrons.

Group 1 cation charge

Alkali metals always make a +1 charge, for example, H+1, K+1.

Group 2 cation charge

Alkaline-earth metals always make a +2 charge, for example, Ca+2, Mg+2.

Group 13 cation charge

Metals always make a +3 charge, for example, Al+3.

Group 15 anion charge

Nonmetals always make a -3 charge by gaining 3 valence electrons, for example, N-3.

Group 16 anion charge

Nonmetals always make a -2 charge by gaining 2 valence electrons, for example, O-2, Se-2.

Group 17 anion charge

Halogens always make a -1 charge by gaining 1 valence electron, for example, Cl-1, Br-1.

Ionic compound charge neutrality

Metal/nonmetal = cation/anion combine to cancel charges, example Al+3Cl-1Cl-1Cl-1 = AlCl3.

Covalent compound formation

Formed by two nonmetals that share valence electrons, example CO2, neutral.

Writing compound formulas

Li2O1 means 2 Li atoms and 1 O atom.

Prefixes for naming compounds

1 mono, 2 di, 3 tri, 4 tetra, 5 penta, 6 hexa, 7 hepta, 8 octa, 9 nona, 10 deca.

Suffix of compound name rule

Goes on the last element name in a compound, for example, dioxide.

Compound naming rules

Capitalize the first element and lowercase others; use prefixes to denote quantities.

Ionic properties

Good conductors, high melting points, highly soluble in water, brittle, and neutral.

Covalent properties

Poor conductors, low melting points, low solubility in water, and neutral.

Balancing equations

Coefficients and subscripts are multiplied for each element to ensure equal atom counts.

Labeling equations example

2Ca + O2 --> 2CaO (Reactants yield Products); subscripts are # of atoms, coefficients are # of molecules.

Is H2O + CO2 → H2CO3 balanced?

Yes, H2O + CO2 → H2CO3 has the same number of atoms of each type on both sides.

Pure substance identification

A pure substance is one type of matter, also an element if all atoms are the same.

Compound identification

A pure substance since it consists of the same molecule/compound.

What does each circle & line represent in a diagram?

Each circle/dot represents an atom and the stick represents the bond between them.

Physical changes description

State change, size and shape change, example melting ice, weathering.

Chemical changes result in

The production of new substances.

Physical changes result in

No new substance is produced.

What charge do compounds have?

Compounds are neutral; charges, if any, cancel out.

Common properties in a group

Elements in a group have common properties due to having the same valence electrons.