Chemistry I Honors 2024-25 Exam #3 Study Guide

Atomic Number of Magnesium

• The atomic number of magnesium is 12, which is determined by the number of protons in its nucleus.

• The atomic mass of an element is the average mass of all its isotopes and is not directly related to the atomic number, which represents the number of protons.

  Number of Neutrons in Magnesium

• The number of neutrons in a magnesium atom can be calculated by subtracting the atomic number (12) from the atomic mass (26).

• Therefore, a magnesium atom has 14 neutrons (26 - 12 = 14).

  Charge of Magnesium Ion

• The magnesium used in the lab is a Mg+2 ion.

• This means it has lost two electrons, resulting in a positive charge of +2.

  Number of Electrons in Cobalt Ion

• Cobalt has an atomic number of 27, indicating 27 protons in its nucleus.

• A cobalt atom with a charge of -1 has gained one electron, increasing its total number of electrons to 28 (27 + 1 = 28).

  Number of Protons in Cobalt

• The atomic mass of cobalt is 58, which is not directly related to the number of protons.

• The number of protons in a cobalt atom is determined by its atomic number, which is 27.

  Number of Valence Electrons in Boron

• Boron has 3 valence electrons.

• Valence electrons are the electrons in the outermost shell of an atom, participating in chemical bonding.

  Electron Configuration of Mg+2

• The electron configuration of Mg+2 is 1s2 2s2 2p6.

• This indicates that magnesium ion has lost its two valence electrons, resulting in a fully filled 2p subshell.

  Dmitri Mendeleev's Contribution to the Periodic Table

• Dmitri Mendeleev, a Russian chemist, developed the first periodic table.

• He organized elements by increasing atomic mass and noticed recurring patterns in their properties, which led to the periodic law.

  Chemical Formula for Ammonia

• The chemical formula for ammonia is NH3, which represents one nitrogen atom bonded to three hydrogen atoms.

  Valence Electrons of Elements

• Group 1 (Alkali Metals): 1 valence electron

• Group 2 (Alkaline Earth Metals): 2 valence electrons

• Group 13 (Boron Group): 3 valence electrons

• Group 17 (Halogens): 7 valence electrons

• Group 18 (Noble Gases): 8 valence electrons (except for Helium, which has 2)

Electronegativity and Periodic Table

• Elements with the highest electronegativity are typically located in the upper right corner of the periodic table.
• Electronegativity is the measure of an atom's ability to attract electrons in a chemical bond.

Nonmetals

• Non-metals are generally poor conductors of heat and electricity.
• They have a tendency to gain electrons, forming anions with negative charges.

IUPAC

• IUPAC stands for International Union of Pure and Applied Chemistry.
• It is a global organization responsible for standardizing chemical terminology and nomenclature, ensuring consistent communication across the scientific community.

Prepare for your Chemistry I Honors Examination #3 with this comprehensive practice exam and study guide. It includes detailed questions on atomic structure and ions, ensuring you understand key concepts before the test date on November 14, 2024.