The Nature of Matter and Chemical Bonds

Comprehensive practice flashcards reviewing atoms, subatomic particles, isotopes, chemical compounds, ionic and covalent bonding, and weak molecular interactions based on textbook pages.

Who first proposed the concept of the atom nearly $2500$ years ago, and from what word is it derived?

The Greek philosopher Democritus proposed the concept of the atom, deriving it from the Greek word atomos, which means "unable to be cut."

How long would a row of $100\text{ million}$ side-by-side surface atoms measure?

It would make a row only about $1\,cm$ long, which is roughly the width of a little finger.

What subatomic particles form the nucleus at the center of an atom, and what binds them together?

Protons and neutrons form the nucleus, bound together by strong forces.

What are the electrical charge and mass of an electron relative to a proton?

An electron is a negatively charged particle ($-$) with only $\frac{1}{1840}$ the mass of a proton.

According to the electron shell diagram, what are the maximum electron capacities for the $K$, $L$, $M$, and $N$ shells?

The $K$ shell can hold up to $2$ electrons ($2e^{-}$), the $L$ shell up to $8$ ($8e^{-}$), the $M$ shell up to $18$ ($18e^{-}$), and the $N$ shell up to $32$ ($32e^{-}$).

What is a chemical element?

A chemical element is a pure substance that consists entirely of one type of atom.

Which six elements make up about $99\%$ of the mass of living things?

Calcium, carbon, hydrogen, oxygen, nitrogen, and phosphorus.

What does the atomic number of an element represent?

The atomic number represents the number of protons in the nucleus of an element's atom.

What are isotopes?

Isotopes are atoms of the same element that differ in the number of neutrons they contain.

How do mass number and atomic mass differ?

Mass number is the total number of protons and neutrons in an atom's nucleus, whereas atomic mass is the weighted average of the masses of an element's isotopes.

Why do all isotopes of an element have the same chemical properties?

Because they have the same number of electrons and protons.

What are the subatomic particle counts and radioactivity status of Carbon-12, Carbon-13, and Carbon-14 as shown in Figure 2-2?

All three have $6$ protons and $6$ electrons. Carbon-12 has $6$ neutrons (nonradioactive), Carbon-13 has $7$ neutrons (nonradioactive), and Carbon-14 has $8$ neutrons (radioactive).

What are three scientific and practical uses of radioactive isotopes?

Geologists use them to determine the ages of rocks and fossils, radiation can kill food-spoiling bacteria or detect cancer, and they serve as tracers/labels to follow substance movements in organisms.

How is the radioactive isotope iodine-131 ($^{131}I$) used to image the thyroid gland?

When injected into the body, iodine-131 concentrates in the thyroid gland at the base of the neck within minutes, allowing a radioactive scan to reveal its location.

What is a chemical compound?

A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions.

How do the physical and chemical properties of a compound compare to those of its component elements?

The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed.

What are valence electrons?

Valence electrons are the electrons in an atom's outer shell that are available to form chemical bonds.

How does an ionic bond form between sodium and chlorine to produce table salt ($NaCl$)?

A sodium atom loses its $1$ outer electron to become a positive sodium ion ($Na^+$), and a chlorine atom gains that electron to become a negative chloride ion ($Cl^-$); these oppositely charged ions attract each other strongly.

What is a covalent bond, and what is the resulting structure called when atoms are joined by covalent bonds?

A covalent bond is formed when moving electrons are shared between atoms; the resulting structure is called a molecule.

How many shared electrons make up single, double, and triple covalent bonds?

A single bond shares $2$ electrons, a double bond shares $4$ electrons, and a triple bond shares $6$ electrons.

What are van der Waals forces, and how do they enable a gecko to climb walls as depicted in Figure 2-7?

Van der Waals forces are slight attractions between nearby matching-shaped molecules; millions of microscopic projections on a gecko's feet maximize surface contact so combined van der Waals forces hold the gecko to walls.

Between which specific atoms do hydrogen bonds form?

Hydrogen bonds form between a hydrogen atom of one molecule and an oxygen or nitrogen atom of a neighboring molecule.