200 things needs to know to Pass the
Chemistry Regents Exam

1. Protons are positively charged (+).
2. Neutrons have no charge.
3. Electrons are small and are negatively charged (-).
4. Protons & neutrons are in an atom’s nucleus (nucleons).
5. Electrons are found in “clouds” (orbitals) around an atom’s nucleus.
6. The mass number is equal to an atom’s number of protons and neutrons added together.
7. The atomic number is equal to the number of protons in the nucleus of an atom.
8. The number of neutrons = mass number – atomic number.
9. Isotopes are atoms with equal numbers of protons, but differ in their neutron numbers.
10. Cations are positive (+) ions and form when a neutral atom loses electrons. They are smaller than their parent atom.
11. Anions are negative ions and form when a neutral atom gains electrons. They are larger than their parent atom.
12. Ernest Rutherford’s gold foil experiment showed that an atom is mostly empty space with a small, dense, positively-charged nucleus.
13. J.J. Thompson discovered the electron and developed the “plum-pudding” model of the atom. + - + - Positive & negative + - + - + particles spread throughout - + - + entire atom. -
14. Dalton’s model of the atom was a solid sphere of matter that was uniform throughout.
15. The Bohr Model of the atom placed electrons in “planet-like” orbits around the nucleus of an atom.
16. The current, wave-mechanical model of the atom has electrons in “clouds” (orbitals) around the nucleus.
17. USE THE REFERENCE TABLES!!!
18. “STP” means “Standard Temperature and Pressure.” (273 Kelvin & 1 atm)
19. Electrons emit energy as light when they jump from higher energy levels back down to lower (ground state) energy levels. Bright line spectra are produced.
20. Elements are pure substances composed of only one kind of atom.
21. Binary compounds are substances made up of only two kinds of atoms. (examples: H2O, NH3, CO2)
22. Diatomic molecules are elements that form two atom molecules in their natural form at STP. Remember the phrase – “BrINClHOF” (Br2, I2, N2, Cl2, H2, O2, F2)
23. Use this diagram to help determine the number of significant figures in a measured value…

Pacific Atlantic

If the decimal point is present, start counting digits from the Pacific (left) side, starting with the first non-zero digit. 1 2 3 0.00310 (3 sig. figs.) If the decimal point is absent, start counting digits from the Atlantic (right) side, starting with the first non-zero digit. 3 2 1 31,400 (3 sig. figs.)
24. Solutions are the best examples of homogeneous mixtures. (Air, salt water, ice tea etc.)
25. Heterogeneous mixtures have discernable components and are not uniform throughout. (Chocolate-chip cookies, vegetable soup, soil, muddy water, etc.)
26. A solute is the substance being dissolved, while the solvent is the substance that dissolves the solute. (Water is the solvent in Kool-Aid, while sugar is the solute.)
27. Isotopes are written in a number of ways: C-14 is also Carbon-14, and is also mass number 14C atomic number 6
28. The distribution of electrons in an atom is its electron configuration.
29. Electron configurations are written in the bottom center of an element’s box on the periodic table in your reference tables.
24.305

Mg

2-8-2
12

# of electrons in 3rd principal energy level (3rd orbital) # of electrons in 2nd principal energy level (2nd orbital) # of electrons in 1st principal energy level (1st orbital)
30. Number of Mole is equal to coefficient number in the equation.

31. Orbital notation is a way of drawing the electron configuration of an atom.

32. Polyatomic ions