sci 2

• Atomic number is the number of protons in an atom
• Mass number is the sum of protons and neutrons in an atom
• Isotopes are atoms with different numbers of neutrons but same atomic number
• John Dalton formulated the Atomic Theory
• Atomic Theory:

  1. All matter is made up of atoms
  2. All atoms in an element are identical
  3. Compounds are made up of atoms of more than one element
  4. A chemical reaction does not involve the creation of destruction of atoms
• A substance is radioactive when it has the ability to emit radiation
• When radioactive substances break down, it forms 3 rays, which are gamma rays, beta rays, and alpha rays
• Gamma rays are made up of particles with no charge
• Alpha rays are made up of particles with positive charges
• Beta rays are made up of particles with negative charge
• An atom with a neutral charge has the same number of electrons and protons
• How do you get the number of neutrons in an atom?

  by subtracting the atomic number from the mass number
• Radiation is the transmission of energy in the form of waves
• The law of definite proportions state that no matter how a compound is formed, it will always have the same ratio of elements by mass
• What does the Law of Conservation of Mass state?

  It states that matter can neither be created or destroyed
• The periodic table is a chart in which elements having similar chemical and physical properties are grouped
• The horizontal rows in the period table are called periods
• The vertical rows in a periodic table are called groups or families
• The elements in the periodic table are categorized into metals, nonmetals, and metalloids
• An aggregate of at least two or more atoms is called a molecule
• A molecule made up of two atoms is called a diatomic molecule
• A molecule made up of three or more atoms is called a polyatomic molecule
• An ion is an atom or group of atom that has a charge, it can either be positive or negative
• An ion that has lost an election contains a positive charge
• An ion that has gained an electron results to a negative charge
• A positive ion is called cation
• A negative ion is called an anion
• An ionic compound is made from a cations and anions
• Ions that only contain one atom are called monoatomic ion
• Ions that are made from multiple atoms are called polyatomic ions
• How many known elements are there?

  92
• these are elements that an organism needs to survive 


  essential elements
• What makes up the volume of an atom?

  Electron cloud
• What makes up majority of the mass of an atom?

  Proton and Neutrons
• What is the difference between elements and compounds?

  Elements are pure substances made up of one type of atom, while compounds are made up of two or more elements
• How is the periodic table organized from left to right and top to bottom?

  Increasing atomic number
• An ionic compound is formed from ionic bonding
• What is the difference between molecules and compounds?

  Molecules can be made by either atoms from one element or by different elements while compounds can only be made by atoms from different elements
• The molecular formula shows the exact number of atoms of each element
• The electron cloud model depicts the wave qualities of an atom