Elements
What is an element
An element is a pure substance that cannot be broken down into simpler substances, consisting of only one type of atom.
What is a compound?
A compound is a pure substance composed of two or more different types of particles (atoms) that are chemically bonded together.
“The symbol ‘Ca’ on the periodic table stands for this element, not carbon.”
Calcium
In the formula H₂O, the small “2” is called this, and it tells you how many atoms of hydrogen are in one molecule of water.
What is a subscript?
An element is made of only one type of atom. A compound is made of two or more ____ chemically combined.
Answer: What are elements?
Elements are found on the Periodic Table. Element examples: Hydrogen, Aluminum, Oxygen, Hydrogen.. etc.
Give an example of a compound.
Ex: Water (H20); Table Salt (NaCl); Carbon Dioxide (CO2), Glucose (C6H12O6)
In the formula HOH, how many hydrogen atoms are present?”
What is 2 hydrogen atoms?
In 2H₂O, the “2” in front of H₂O is called this, and it tells you how many molecules are present
What is a coefficient?
Which of these is an element: NaCl or O₂?
How do you know?
What is O₂?
What represents elements on the Periodic Table?
Chemical Symbols
How is a compound formed?
A compound is formed when two or more different atoms bond chemically.
True or False: A missing subscript always means there are zero atoms of that element.”
False, (It means one atom.)
In the formula Ca(OH)₂, the “₂” outside the parentheses applies to both O and H, meaning there are how many oxygen atoms and how many hydrogen atoms?
What are 2 oxygen atoms and 2 hydrogen atoms?
True or False — Compounds can be broken down into simpler substances, but elements cannot.
What is True?
Misconception Check! True or false: Oxygen gas (O2) is a compound because it has two atoms.
False!
It is still an element, the 2 represents a subscript for ONLY Oxygen
What does the subscript in H2O tell you?
The subscript '2' in H2O indicates that there are two hydrogen atoms in each
Name this element!
This element’s symbol has two letters, starts with an N, and it’s found all the way on the right side of the periodic table with the other gases that don’t like to bond. It glows in bright signs downtown.
Symbol: Ne
Atomic Number: 10
Category: Noble Gas (far right column of the periodic table)
Properties: Colorless, odorless gas that glows bright orange-red in signs when electricity passes through it.
Connection: The bright lights you see in “neon signs” are this element.
In CO, the oxygen has no subscript. That means there is how many oxygen atoms in one molecule of CO?
What is 1 oxygen atom?
Salt (NaCl) is a compound, and oxygen gas (O₂) is an element. Explain the difference in how many types of atoms each contains.
NaCl has 2 different types of atoms (Na and Cl). O₂ has only 1 type of atom (O).
True or False:
Each element is made up of only one type of atom.
True!
How can you tell the number of elements in a chemical formula?
Count the capital letters!
One or two. They always start with a capital letter and the second letter is always lowercase.
True or False — CO and CO₂ are the same compound because they both contain carbon and oxygen.
What is False? (They are different compounds with different properties.)
Water (H₂O) and hydrogen gas (H₂) both contain hydrogen. Why is one a compound and the other an element?
H₂O has 2 different elements (H and O), so it’s a compound. H₂ has only hydrogen, so it’s an element.