1. Chapter 4 Middle School Chemistry
Periodic Table
Chapter 4
Middle School Chemistry

3. Salt (NaCl), sodium chloride, mineral substance of great importance.

4. WATER H2O is Water (H2O, HOH) is the most abundant molecule on Earth's surface, composing 70-75% of the Earth's surface as liquid and solid state in addition to being found in the atmosphere as a vapor. It is in dynamic equilibrium between the liquid and vapor states at standard temperature and pressure. At room temperature, it is a nearly colorless, tasteless, and odorless liquid.

5. Carbon Dioxide (chemical formula CO2) is a colorless, odorless gas vital to life on Earth.

6. Protons – Neutrons - Electrons
Protons are located in the nucleus of the atom. A proton has a positive charge.
Neutrons are in the nucleus of the atom. A neutron has no charge.
An electron is in a region outside the nucleus. An electron has less mass than a proton and has a negative charge

7. The atomic number of an atom is the number of protons.

8. Isotopes https://search. yahoo. com/yhs/search
The atoms of the same element can have different isotopes. An isotope of an atom is an atom with a different number of neutrons.
Atomic Mass
The atomic mass of an element is the average mass of all the isotopes of the element.

9. In the Lewis dot diagram, the electrons shown are in the outermost energy level.

10. A hydrogen atom is made up of one proton and one electron
A hydrogen atom is made up of one proton and one electron. The proton and electron positive and negative charges attract.

11. An electron is in a region outside the nucleus.
Protons and electron are attracted to one another.
The atomic number of an atom is equal to the number of protons in the atom’s nucleus.

12. Different atoms of the same element can have a different number of neutrons.
The electrons of an atom are located in regions around the nucleus called energy levels. The first energy level of an atom is closest to the nucleus.

13. Lewis Dot Structure A way of representing atoms or molecules by showing electrons as dots surrounding the element symbol. A shorthand way of showing only the valence electrons of an atom.

14. The atoms in a column of the periodic table all have the same number of electrons in the outer energy level.
In the process of covalent bonding, atoms share electrons. This means that electron for each atom are attracted to the nucleus of both atoms.

15. How Ions Form
An ion is an atom or group of atoms that has an electric charge. When an atom loses an electron, it loses a negative charge and becomes a positive ion. When an atom gains an electron it gains a negative charge and becomes a negative ion.

16. An ion is an atom that has gained or lost one of more electrons
An ion is an atom that has gained or lost one of more electrons. An ion is formed when one atom has a stronger attraction for electrons than the other atom, which causes one or more electrons to be transferred to the atom with a stronger attraction. An atoms that loses an electron becomes a positively charged ion and the atom gains an electron becomes a negatively charge ion. Since atoms start with the same number of protons as electrons, an atom that loses an electron will have one extra proton and be positive. The atom that gained the electron will have an extra electron and be negative. Ionic Bonding In the process of ionic bonding, ions come together because positive and negative ions attract. In the process of ionic bonding one atom gains one or more electrons and the other loses the same number.

17. Valence Electron Valence electron are those electrons that have the highest energy level and are held most loosely. The electron on the outermost energy level of an atom is called valence. The number of valence electrons in an atom of an element determines many properties of that element, including the way in which the atom can bond with other atoms. Electron dot diagram: Each element has specific number of valence electrons ranging from 1 to 8. An electron dot diagram includes the symbol for the element surrounded by dots. Each dot stands for on valence electron.

18. An atom with 8 electrons in the periodic table also has 8 protons and that is oxygen.