1.4.1 Writing Chemical Formulae

• What does a chemical formula describe in terms of atoms?

  The ratio of atoms
• What is the atomic number of helium?

  2
• What do chemical formulae represent in chemistry?

  Compounds and molecules
• What is the atomic number of calcium?

  20
• A compound is made of two or more identical elements chemically bonded together.

  False
• What is the atomic number of beryllium?

  4
• What is the atomic number of potassium?

  19
• What is the atomic number of scandium?

  21
• What is the atomic number of titanium?

  22
• Order the elements from left to right in the periodic table based on their classification:

  1️⃣ Metals

  2️⃣ Metalloids

  3️⃣ Non-metals
• What is the atomic number of vanadium?

  23
• How many oxygen atoms are in a molecule of water?

  One
• What is the atomic number of magnesium?

  12
• What are the chemical formulas for the following molecules?

  • Oxygen (O₂)
  • Carbon dioxide (CO₂)
  • Nitrogen (N₂)
  • Ammonia (NH₃)
• What is the atomic number of lithium?

  3
• What is the atomic number of sodium?

  11
• What are the chemical formulas for the following organic molecules?

  • Methane (CH₄)
  • Ethane (C₂H₆)
  • Ethene (C₂H₄)
• What is the charge of a sodium ion (Na)?

  +1
• What type of bonds hold atoms together in a molecule?

  Covalent bonds
• What is the atomic number of argon?

  18
• How many hydrogen atoms are in a molecule of water?

  Two
• What is the chemical formula for Calcium Chloride?

  CaCl₂
• What is the chemical formula for hydrogen chloride?

  HCl
• What is the chemical formula for chlorine?

  Cl₂
• What must the total positive and negative charges in an ionic compound equal to ensure it is electrically neutral?

  Zero
• What is the atomic number of phosphorus?

  15
• How are covalent compounds formed?

  Atoms share electrons
• Match the terms with their definitions:

  Group ↔️ Vertical column

  Period ↔️ Horizontal row

  Atomic number ↔️ Number of protons
• Match the ion with its charge:

  Calcium ↔️ +2

  Chloride ↔️ -1
• What is the atomic number of sulfur?

  16
• What is the atomic number of silicon?

  14
• How many carbon atoms are in carbon dioxide?

  One
• What is the first letter of an element symbol always?

  Capitalized
• Match the group number with the corresponding ion charge:

  Group 1 ↔️ +1

  Group 2 ↔️ +2

  Group 6 ↔️ -2

  Group 7 ↔️ -1
• What is the balanced formula for Magnesium Oxide, where Mg²⁺ has a +2 charge and O²⁻ has a -2 charge?

  MgO
• What is the atomic number of chlorine?

  17
• What is the first step in writing chemical formulae for ionic compounds?

  Identify the ions
• What is the chemical formula for dinitrogen pentoxide?

  N₂O₅
• What separates metals from non-metals in the periodic table?

  Staircase line
• What is the chemical formula for water?

  H₂O