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Transcript of Chemistry
Ions are atoms with an uneven number of protons and electrons, giving the atom either a positive or negative charge.
Atoms & Ions
The chemical symbol of an atom is made up of either one upper-case letter and one lower-case letter or one upper-case letter by itself. Ions are represented by the small plus or minus symbol in the upper-right corner of the box.
Chemical symbols for atoms & ions
Polyatomic ions are essentially chemical compounds with a charge (+/-). For example, CO (carbonate).
Identify dependent, independent, and control variables taken from a scientific study.
Explain the importance of control variables in answering a scientific question.
The reason why control variables are important is so you can track how results in the experiment/question are changed depending on the variables.
Identify and describe the three subatomic particles that make up the atom including their properties and location in the atom. Represent the atomic structure for the first 20 elements using Bohr model diagrams.
Variables & Structure
Independent variables will not be affected by other variables. The variable that you purposely change.
Negatively charged and fast moving
Surrounds the nucleus
Smaller than protons
Make up the nucleus
Shows the number of electrons in each of the energy levels around an atom
Electron Shells: energy level
1st shell: 2 electrons
2nd and 3rd shell: 8 electrons
Valence Shell: the shell on the outside
Valence Electrons: the electrons on the valence shell
The periodic table is placed based on the element’s chemical and physical properties. In each box of the table contains:
1. the name of the element under the chemical symbol
2. the chemical symbol of the element
3. the atomic number of the element on the upper left corner. (the number of protons in the nucleus of each one of its atoms
4.the average atomic mass of the element under the name. (the weighted average of the masses of the atoms of an element.
5.the ion charge of the element on the upper right side of the box. ( an element can have multiple ion charges)
Organization of the Periodic Table
A physical change in a substance doesn't change the matter or what the substance is made of. An example is a melting popsicle. In a chemical change where there is a chemical reaction, a new substance is formed and there is energy present. An example is fireworks exploding.
Difference between Chemical and Physical Change
Periodic Table and Properties
Dependent variables depend on the independent variables (hence the name).
Controls are unchanging variables. That should be same for both experimental group and control group.
Atoms are made up of 3 subatomic particles:
electron, protons, and neutrons
Neutral w/ no charge
Make up the nucleus
: If the control variable is not the
same for both experimental and control
group, then it is unclear of what
changed the result.
A monatomic ion, however, is an element with a charge. These are formed when the valence shell of the element is not complete. The element will either lose or gain electrons to achieve a full valence shell. (elements with 4 valence electrons are not likely to do this because they will either have to gain or lose 4 electrons). For example, lithium will lose one valence electron to achieve a full outer shell.
By Claire, Matina, Liza, Anika, Victoria
Chemical formulae for ionic compounds
chemical formula of an ionic compound includes symbols that identify each ion in the compound
ionic compounds with multivalent metals include roman numerals (they can form two or more different positive ions with different charges)
Formulas of ionic compounds with 2 elements
1. What is the definition of a control variable?
2. Give an example of a chemical change.
3. Write the chemical formulas for the following compounds (use your periodic table):
eg: zinc nitride
1. identify each ion and its charge → zinc: Zn nitride:N
2. determine the total charges needed to balance the positive and negative ions → Zn :2+2+2=6 N :3+3=6
3. use subscripts to write formula. Note that “1” is not shown in subscript → Zn3N2
Formulas of compounds with multivalent metal
eg: iron(III) sulphide
1. identify each ion and its charge→ iron(III):Fe sulphide:S
2. determine the total charges needed to balance the positive and negative ions. → Fe :3+3=6 S :2+2+2=6
3. use subscripts to write the formula → Fe2S3
Formulas for compounds with polyatomic ions
eg: ammonium carbonate
1. identify each ion and its charge → ammonium:NH4 carbonate:CO3
determine the total charges needed to balance the positive and negative ions → NH4 :1+1=2 CO3 :2-
3. use subscripts and brackets to write the formula. Omit brackets if only one
ion is needed →(NH4)2CO3
The chemical symbol of the cation is always written first, followed by the anion. If they do not have the same charge, they must even out. For example, if the cation has a charge of 2 and the anion 1, you will have to write 2 in subscript after the anion