1.1 Atoms, elements, and compounds

• What is the smallest unit of an element that retains its chemical properties?

  Atom
• What type of charge do electrons have?

  Negative
• What does the atomic number of an element represent?

  Number of protons
• Steps to calculate the number of neutrons in an atom

  1️⃣ Identify the atomic number

  2️⃣ Identify the mass number

  3️⃣ Subtract the atomic number from the mass number
• A compound is made of two or more elements chemically bonded together.


  True
• Reactivity increases as you move down a group in the periodic table.


  True
• An atom consists of a central nucleus containing protons and neutrons.
• Match the component of an atom with its location, charge, and relative mass:

  Proton ↔️ Nucleus, +1, 1 amu

  Neutron ↔️ Nucleus, 0, 1 amu

  Electron ↔️ Electron cloud, -1, Negligible
• The mass number is approximately equal to the atomic mass of an atom.


  True
• Elements in the periodic table are arranged based on their chemical properties and atomic mass.

  False
• Arrange the periodic trends in order based on how they change across a period:

  1️⃣ Atomic Number: Increases by 1

  2️⃣ Reactivity: Decreases

  3️⃣ Electronegativity: Increases

  4️⃣ Ionization Energy: Increases
• What are the three isotopes of hydrogen?

  Protium, deuterium, tritium
• What is a compound made of?

  Two or more elements
• Compounds retain the chemical properties of their individual elements.

  False
• Compounds can be broken down into simpler substances by chemical means.

  True
• What charge do protons have?

  Positive
• What is the charge of a neutron?

  Neutral
• What is an element arranged in the periodic table based on?

  Atomic number
• What are the two main properties used to organize the periodic table?

  Atomic number and chemical properties
• Reactivity generally decreases across a period and increases down a group
• Hydrogen has three isotopes: protium, deuterium, and tritium
• Compounds retain the chemical properties of their individual elements.

  False
• Protons have a relative mass of 1 amu and determine the atomic number of an element.


  True
• Protons are positively charged particles located in the nucleus.


  True
• Hydrogen has an atomic number of 1 because it has 1 proton in its nucleus.


  True
• What happens to atomic number as you move across a period in the periodic table?

  Increases by 1
• The reactivity of elements decreases as you move down a group in the periodic table.

  False
• Electrons have a relative mass of 1 atomic mass unit (amu).

  False
• To calculate the number of neutrons in an atom, you subtract the atomic number from the mass number.
• What is the definition of an element?

  Pure substance of one atom
• How does the reactivity of elements change as you move down a group?

  Increases
• Isotopes of an element have the same number of neutrons.

  False
• Match the compound with its chemical formula:

  Water ↔️ H2O

  Carbon dioxide ↔️ CO2

  Salt ↔️ NaCl
• An element is a pure substance made of one type of atom
• Sodium chloride is commonly known as table salt
• Atoms consist of a central nucleus containing protons and neutrons
• The atomic number of an element is determined by the number of protons
• Carbon has an atomic number of 6 and a mass number of 12, meaning it has 6 neutrons
• Arrange the following periodic trends in order as you move across a period from left to right:

  1️⃣ Atomic Number increases

  2️⃣ Reactivity decreases

  3️⃣ Electronegativity increases
• Isotopes of the same element have the same number of protons but a different number of neutrons.


  True