BIOL 1710 Chapter 2

Flashcards covering isotopes, atomic mass, electron structure (shells, subshells, orbitals), electron configuration, bonding (covalent, ionic, polar vs nonpolar), diatomic molecules, and related concepts from the lecture notes.

What is an isotope?

Atoms of the same element with different numbers of neutrons, resulting in different mass numbers.

Why is the atomic mass on the periodic table not a whole number?

Because it is a weighted average of the naturally occurring isotopes, producing decimals.

What are the common natural isotopes of chlorine and their approximate abundances?

Cl-35 (~75%) and Cl-37 (~25%), giving a weighted average around 35.4.

How do you calculate the weighted average atomic mass from isotopes?

Multiply each isotope’s mass by its fractional abundance, then sum the results.

What is the outermost electron shell called?

The valence shell.

What are the labels used for subshells in atomic structure?

s, p, d, and f.

How many orbitals and electrons can be held in the s subshell?

1 orbital, up to 2 electrons.

How many orbitals and electrons can be held in the p subshell?

3 orbitals, up to 6 electrons.

How many orbitals and electrons can be held in the d subshell?

5 orbitals, up to 10 electrons.

How many orbitals and electrons can be held in the f subshell?

7 orbitals, up to 14 electrons.

What is an orbital?

A region where an electron sits; each orbital holds 2 electrons; subshells contain orbitals; shells contain subshells.

What is the Aufbau principle?

Electrons fill the lowest energy levels first before higher ones (e.g., 2s before 2p).

What is the maximum number of electrons in the first shell?

2 electrons (1s).

What are valence electrons?

Electrons in the outermost shell that participate in bonding.

What is the octet rule?

Most atoms strive for eight electrons in the valence shell to be stable (Hydrogen and Helium are exceptions).

What is a covalent bond?

A bond formed by sharing electrons between atoms.

What distinguishes polar covalent bonds from nonpolar covalent bonds?

Polar covalent bonds involve unequal sharing of electrons; nonpolar covalent bonds involve equal sharing.

What is an ionic bond?

A bond formed by transfer of electrons, creating positively and negatively charged ions.

What is a Lewis dot structure?

A diagram showing valence electrons as dots around the element symbol to illustrate octet or valence electron count.

Which elements are commonly diatomic in nature and typically found as diatomic molecules?

Hydrogen (H2), Nitrogen (N2), Oxygen (O2), Fluorine (F2), Chlorine (Cl2), Bromine (Br2), Iodine (I2).

What happens to electrons during ion formation in terms of which shell is affected?

Electrons are removed from the outermost (valence) shell first.

Why is 4s filled before 3d in some electron configurations?

Because the 4s subshell lies at a lower energy level than the 3d subshell, so it is filled first.

What happens if you remove electrons to form Na+?

Na+ achieves a noble-gas-like electron configuration (same as Ne).