Mastering Biology Chapter 2 Flashcards

Atoms and Elements

• An element is a fundamental substance that cannot be broken down into simpler substances through chemical means.
• Protons carry a positive charge (+1) and are denoted by the symbol p.
• Neutrons have no charge (0) and are represented by the symbol n.
• Electrons possess a negative charge (-1) and use the symbol e.

Atomic Mass and Structure

• Protons and neutrons each have a mass of approximately 1 atomic mass unit (amu).
• Electrons have a negligible mass, approximately 1/2000 amu.
• The mass number for an ion with 104 electrons, 158 neutrons, and a +1 charge is 263.
• The innermost electron shell of an atom can accommodate a maximum of 2 electrons.

Charged Atoms and Isotopes

• An uncharged atom contains an equal number of protons and electrons.
• The atomic number of an atom with 6 protons, 6 neutrons, and 6 electrons is 6.
• Atoms with the same atomic number but different atomic masses are known as isotopes.
• Fluorine, with an atomic number of 9 and atomic mass of 19, has 10 neutrons.

Electron Configuration

• An uncharged atom of boron, with an atomic number of 5 and atomic mass of 11, has 5 protons.
• Changing the number of protons in an atom transforms it into a different element.
• Different isotopes of phosphorus have varying numbers of neutrons.

Chemical Bonding

• The nature of bonding and the number of covalent bonds an atom can form depend on the number of unpaired electrons in the valence shell.
• A bond joining two hydrogen atoms is a covalent bond.
• A molecule is formed when two or more atoms are held together by covalent bonds.
• Carbon can form up to 4 single covalent bonds.
• A double covalent bond occurs between two oxygen atoms.

Ionic Bonds

• Atoms with the same number of protons but different electrical charges are classified as ions.
• In sodium chloride (salt), the bond between sodium and chlorine is ionic.
• The result of interactions in salt formation is a positively charged sodium ion and a negatively charged chlorine ion.
• An ionic bond arises from the attraction between ions of opposite charges.

Types of Bonds in Molecules

• Carbon and hydrogen form a single (nonpolar) covalent bond.
• Hydrogen bonds, indicated by brackets, label interactions between molecules like water.
• The bond between water molecules is also a hydrogen bond.
• An ionic bond occurs when one atom transfers an electron to another.

Chemical Equilibrium and Electron Orbitals

• Chemical equilibrium is established when forward and reverse reactions take place at the same rate, maintaining constant reactant and product concentrations.
• An electron orbital describes the three-dimensional region where an electron is likely to be found 90% of the time.
• A chemical bond forms when two atoms either transfer or share outer electrons to complete their valence shells.

Characteristics of Weak Bonds

• Weak bonds are typically transient and easily reversible, allowing for dynamic interactions in molecular biology.

Test your knowledge of key terms and concepts from Chapter 2 of Mastering Biology. This quiz covers essential definitions and symbols associated with fundamental biological elements. Perfect for reinforcing your understanding of basic biology concepts.