Unit 1: Chapter 2 Flashcards
What is an element?
is a substance that cannot be broken down to other substances by chemical reactions.
What is a compound?
is a substance consisting of two or more different elements combined in a fixed ratio.
What are essential elements?
- Of the 92 natural elements, about 20–25% are that an organism needs to live a healthy life and reproduce.
- Make up approximately 96% of living matter.
- oxygen (O),
- carbon (C),
- hydrogen (H), and
- nitrogen (N)—
- 4 % make up the rest of the mass on earth
- Calcium (Ca),
- phosphorus (P),
- potassium (K),
- sulfur (S),
How can medicine use isotopes to help diagnose disease?
Radioactive isotopes are often used as diagnostic tools in medicine.
What dictate the chemical behavior of an atom?
- depends mostly on the number of electrons in its valence shell.
What is a polar covalent bond?
electrons of the bond are not shared equally. This type of bond is called a polar covalent bond.
What is an ionic bond?
Because of their opposite charges, cations and anions attract each other; this attraction is called an ionic bond.
Environment affects the strength of ionic bonds.
- In a dry salt crystal, the bonds are strong
- In water, ionic bonds are much weaker because each ion is partially shielded by its interactions with water molecules.
Describe a hydrogen bond
- a hydrogen atom is covalently bonded to an electronegative atom, the hydrogen atom has a partial positive charge that allows it to be attracted to a different electronegative atom nearby. This attraction between a hydrogen and an electronegative atom is called a hydrogen bond.
What is molecular shape important?
Molecular shape is crucial:
- determines how biological molecules recognize and respond to one another with specificity.
- Biological molecules often bind temporarily to each other by forming weak interactions, but only if their shapes are complementary.
