Atomic Basics
What is Matter?
Anything that has mass and takes up space (volume).
What are the three main subatomic particles inside an atom?
Protons, neutrons, electrons.
What is an atom?
The basic building block of all matter; smallest unit of an element.
What is a Bohr model?
A Bohr model is a diagram showing an atom with a central nucleus and electrons orbiting in shells.
What is the first step of the scientific method?
Ask a question, identify the problem or make an observation that can be tested.
Name the Three States of Matter
Solid, Liquid, Gas
Where are protons, neutrons, and electrons located in an atom?
Protons and neutrons: inside the nucleus. Electrons: in the electron cloud (shells) around the nucleus.
Give an example of a chemical formula (write a common one).
Example: H2O or CO2.
Where is the nucleus located in an atom, and which particles are inside it?
The nucleus is at the center of the atom; it contains protons and neutrons.
What is a hypothesis? AND give an example
A hypothesis is an educated guess that predicts the outcome of an experiment; it is usually written as an if–then statement. Example: "If I heat ice, then it will melt faster."
What is the difference between an element and a compound?
Element: only one kind of atom. Compound: two or more different elements chemically combined.
What electrical charge does each subatomic particle have?
Protons: positive (+). Neutrons: neutral (0). Electrons: negative (−).
What is a subscript in a chemical formula and what does it tell us?
A subscript is the small number written to the lower-right of an element symbol in a formula; it tells how many atoms of that element are present.
How many electrons fit on the 1st electron shell?
1st shell: up to 2 electrons.
What is the difference between an independent variable and a dependent variable?
Independent variable: the factor the experimenter changes on purpose. Dependent variable: the factor that is measured or observed and may change because of the independent variable.
What is a molecule? Give one example.
Molecule: two or more atoms bonded together (example: H2OH2O or O2O2). (Represented by Coefficient)
How does the number of protons define an element?
The number of protons (atomic number) determines which element it is.
How do you find protons and electrons from the atomic number on an element tile for a neutral atom?
Protons = Atomic number. Electrons = Atomic number (if the atom is neutral).
How many electrons can fit on the 2nd and 3rd shells (combined limits commonly taught for basic shell filling)?
2nd shell: up to 8 electrons; 3rd shell: up to 18.
What are constants in an experiment, and why are they important?
Constants are the factors that are kept the same in all trial groups so they do not affect the outcome. They are important because they ensure that any change in the dependent variable is caused by the independent variable, not by other differences between trials.
Where are the atomic number and atomic mass listed on a typical element tile?
Atomic number is at the top of the element tile; atomic mass is at the bottom (often a decimal).
How do you find the number of neutrons using the atomic mass and atomic number? (Write the calculation method.)
Neutrons = Rounded atomic mass − Atomic number (e.g., Neutrons = 16 − 8 = 8 for oxygen).
Explain the difference between a chemical symbol and a chemical formula.
A chemical symbol is the one- or two-letter shorthand for an element (e.g., O for oxygen). A chemical formula shows which elements and how many atoms of each are in a compound (e.g., H2O).
Draw (or describe clearly) a simple Bohr model for oxygen (atomic number 8): show the number of protons, neutrons (use rounded mass 16), and electrons in each shell.
Bohr model for oxygen (atomic number 8, mass ~16): Nucleus: 8 protons and 8 neutrons. Electrons: 2 in the 1st shell, 6 in the 2nd shell. (If drawing, place 8 in nucleus labeled +/0 and show shells with 2 and 6 electrons.)
Give an example of a testable hypothesis about how temperature affects the state of matter, and identify the independent variable, dependent variable, and one control.
Example hypothesis: "If water temperature increases, then the time it takes for ice cubes to melt will decrease."