Chemical Basis of Life Flashcards
What is matter made up of?
Elements (basic substances)
What is the nucleus surrounded by?
Electrons
What subatomic particle is represented by an element’s atomic number?
Protons. The atomic number represents the amount of protons found in the nucleus of an atom of that element.
What charge do electrons, protons, and neutrons have?
Electrons have a charge of -1. Protons have a charge of +1. Neutrons have no charge (they are neutral as per the name).
In an uncharged atom, the number of protons is equal to the number of what?
Electrons
What is an electron cloud?
A three-dimensional space in which electrons travel freely. The electron cloud is made up of energy levels/energy shells and orbitals.
What is the energy level closest to the nucleus?
- The number increases as we get farther away from the nucleus.
Which energy level has the most energy?
The energy level farthest from the nucleus.
How many electrons can the inner shell have? How many electrons can the subsequent (valence) shells have?
The innermost shell can have maximum 2 electrons. Valence shells/the outer shells of the electron can have a maximum of 8 electrons.
What makes an atom stable?
They are more stable when every electron is paired and most stable when their valence level is full.
Which atoms are unstable?
Atoms with unpaired or partially filled valence levels. These atoms will easily gain or lose electrons in order to obtain a more stable configuration.
What is a covalent bond?
A bond formed between atoms when they share electrons. They are the strongest type of chemical bond. They result in a molecule.
What is a molecule?
Two or more atoms held together by covalently shared electrons.
What is a compound?
A compound is formed when two or more different atoms bond together chemically to create a unique substance (e.g., H2O, CH4).
What results in a molecular element?
Two atoms of the same element covalently bonded (e.g., O2).
What are charged atoms called?
Ions
How can an uncharged electron become more stable?
- An uncharged electron may be more stable if its valence level loses one or more electrons and becomes positively charged. It becomes a positively charged particle or a positive ion.
- Similarly, an atom that gains one or more electrons to fill its valence level becomes a negative ion.
What is an ionic bond?
- Negative and positive ions, being oppositely-charged, are attracted to each other which forms an ionic bond (e.g., NaCl [sodium chloride/table salt]).
- Weaker than covalent bonds
What makes a molecule polar?
- Having regions of partial charge (e.g., a molecule with a weak, partial negative in one region of the molecule and a partial positive charge in another region).
Describe a hydrogen bond
- Hydrogen bonds are formed between water molecules.
- Water molecules (with a net charge of 0) have a partial negative charge near the oxygen atom and a partial positive charge near each of the hydrogen atoms.
- When water molecules are close together, their positive regions are attracted to the negatively charged regions of nearby regions , vice versa. The force of attraction is a hydrogen bond.
- A weak chemical bond that temporarily holds separate molecules together.
When do chemical reactions occur?
- Chemical reactions occur when molecules interact with each other to form one or more molecules of another type.
- Chemical reactions that occur within the cell provide energy, nutrients, and other products that allow the organism to function.
Describe the composition of a chemical reaction equation
Chemical reactions are symbolized by an equation where the reaction molecules (reactants) are shown on the left side and newly formed molecules (products) are on the right side, with an arrow indicating the direction of the reaction.
What does a decomposition reaction look like?
AB —> A +B
What does a simple combination reaction look like? (Reverse of decomposition)
A +B —> AB
