CHEM 1151 Chapter 2 Atoms and the Periodic Table

What is an element?

A pure substance that cannot be broken down into simpler substances by a chemical reaction.

What are the three main classifications of elements based on their properties?

Metals, nonmetals, and metalloids.

What describes the structure of an atom?

Atoms are composed of protons, neutrons, and electrons, with protons and neutrons forming the nucleus and electrons occupying the electron cloud.

What is the definition of isotopes?

Atoms of the same element that have a different number of neutrons.

How is the atomic weight of an element calculated?

It is the weighted average of the masses of the naturally occurring isotopes of that element.

What is the significance of an element's position in the periodic table?

It indicates the element's chemical properties and its classification as a metal, nonmetal, or metalloid.

What are valence electrons?

Electrons in the outermost shell of an atom that determine its chemical properties.

What is ionization energy?

The energy needed to remove an electron from a neutral atom.

How does atomic size change across a period?

Atomic size decreases as you move from left to right across a period due to increasing nuclear charge.

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

2 electrons.

Describe the concept of noble gas notation.

A shorthand way to write electron configurations using the symbol for the nearest noble gas to represent inner-shell electrons.

What are the four building-block elements of the human body?

Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N).

What are alkali metals?

Elements in Group 1A of the periodic table that are soft, shiny metals with low melting points.

What is the difference between a cation and an anion?

A cation is a positively charged ion, while an anion is a negatively charged ion.

What characterizes metalloids?

Elements with properties intermediate between metals and nonmetals, located along the 'stair-step' line of the periodic table.