Chapter 4 - Atoms and Elements

4.1 - Elements and Symbols

• Primary substances of matter are elements.
• Chemical symbols are abbreviations of element names in a single or two-letter way.

4.2 - The Periodic Table

• A periodic table is a table of elements with the atomic numbers increasing while going through the table.
  • Horizontal rows in the table are called periods.
• An element with similar properties is called a group in the vertical column on the periodic table.
• Group 1a(1) is known as alkali, Group 2A(2) is referred to as alkaline earth, Group 7A(17) is known as halogens, and Group 8A(18) contains noble gasses.
  • The metals are on the left side of the heavy zigzag line on the periodic table and nonmetals are on the right-hand side of the heavy zigzag line.
  • With the exception of aluminum, metalloids are called elements along the heavy zigzag line.

4.3 - The Atom

• An atom is the smallest particle to preserve an element's characteristics
• Three kinds of subatomic particles consist of atoms
  • Positive protons (+), negative charges of electrodes (-), and electrically neutral neutrons.
• In the small, dense nucleus, the protons and neutrons are found; electrons are outside the nucleus.

4.4 - Atomic Number and Mass Number

• In all atoms in the same element, the atomic number indicates the number of protons.
  • The number of protons and electrons in a neutral atom is identical
• The total number of protons and neutrons in a nucleus is the mass number.

4.5 - Isotopes and Atomic Mass

• Isotopes are atoms that have the same proton number, but various neutron numbers.
• The element's atomic weight consists of the average mass of all isotopes in a natural sample.

4.6 - Electron Energy Levels

• Each electron is energy-specific.
  • Electrons of similar energy in an atom are grouped into specific levels of energy.
• The second level holds up to 8 electrons and the third level holds up to 18 electrons.
  • The first level is closest to the core.
• The arrangement of electrons is written in order to place the number of electrons in this atom from the lowest energy level to the highest.

4.7 - Trends in Periodic Properties

• The element characteristics are linked to atom valence electrons.
  • With only a few exceptions, the same arrangement of valence electrons only differs in energy level for each group of elements
• The electrons of Valence are represented as points around the element symbol
• The size of an atom increases from left to right over a period, going down a group.
  • The energy needed to remove a valence electron is the energy of ionization, which decreases over time and goes from left to right.
• The metallic nature of an element increases the number of people going down and decreases throughout a period from left to right.