Composition of matter
What is matter?
Anything that occupies space or has mass
What is a chemical symbol?
A unique symbol for each element, consisting of 1-2 letters.
What is the nucleus of an atom?
The central core containing protons and neutrons.
How many electrons can the K energy level hold?
2 electrons.
What is a chemical equation?
a representation of a chemical reaction using symbols.
What is the difference between mass and weight?
Mass is the quantity of matter, while weight is the pull of gravity on an object.
What is the atomic number?
The number of protons in an atom of an element.
What particles are found in the nucleus?
Protons and neutrons.
According to the octet rule, how many electrons can levels L-Q hold?
8 electrons.
What are reactants and products in a chemical equation?
Reactants are on the left side, and products are on the right side of the equation.
What are the two main types of pure substances?
Elements and compounds.
What are isotopes?
Atoms of the same element with different numbers of neutrons.
How do electrons behave in relation to the nucleus?
They travel at high speeds at various distances from the nucleus.
What determines the state of matter?
the rate of motion of atoms or molecules
What is activation energy?
The energy needed to start a chemical reaction.
: How many elements are naturally occurring?
92 naturally occurring elements.
Why do elements combine to form compounds?
Because most elements are not stable in their natural state.
What are energy levels in relation to electrons?
The regions where electrons are found at varying distances from the nucleus.
What happens to a substance when thermal energy is added?
It may change state (e.g., solid to liquid)
What is the difference between exergonic and endergonic reactions?
Exergonic reactions release energy, while endergonic reactions absorb energy.
What makes up 90% of the mass of an organism?
Oxygen, carbon, hydrogen, and nitrogen.
What is the significance of the arrangement of elements in the periodic table?
Elements are arranged by atomic number, indicating their properties and relationships.
How many energy levels do atoms have?
7 energy levels.
What is the role of energy in chemical reactions?
It is necessary to break bonds and rearrange atoms during reactions.
What are enzymes and their role in reactions?
Enzymes are biological catalysts that speed up reactions by lowering activation energy.