Question

For each of the following elements, write its chemical symbol, locate it in the periodic table, give its atomic number, and indicate whether it is a metal, metalloid, or nonmetal: (a) chromium, (b) helium, (c) phosphorus, (d) zinc, (e) magnesium, (f) bromine, (g) arsenic.

Short answer

(a) Chromium: Cr, Group 6, Period 4, Atomic number 24, Metal. (b) Helium: He, Group 18, Period 1, Atomic number 2, Nonmetal (noble gas). (c) Phosphorus: P, Group 15, Period 3, Atomic number 15, Nonmetal. (d) Zinc: Zn, Group 12, Period 4, Atomic number 30, Metal. (e) Magnesium: Mg, Group 2, Period 3, Atomic number 12, Metal (alkaline earth metal). (f) Bromine: Br, Group 17, Period 4, Atomic number 35, Nonmetal (halogen). (g) Arsenic: As, Group 15, Period 4, Atomic number 33, Metalloid.

Step-by-step solution

(a) Chromium

- Chemical symbol: Cr - Located in the periodic table: Group 6, Period 4 - Atomic number: 24 - Classification: Metal

(b) Helium

- Chemical symbol: He - Located in the periodic table: Group 18, Period 1 - Atomic number: 2 - Classification: Nonmetal (noble gas)

(c) Phosphorus

- Chemical symbol: P - Located in the periodic table: Group 15, Period 3 - Atomic number: 15 - Classification: Nonmetal

(d) Zinc

- Chemical symbol: Zn - Located in the periodic table: Group 12, Period 4 - Atomic number: 30 - Classification: Metal

(e) Magnesium

- Chemical symbol: Mg - Located in the periodic table: Group 2, Period 3 - Atomic number: 12 - Classification: Metal (alkaline earth metal)

(f) Bromine

- Chemical symbol: Br - Located in the periodic table: Group 17, Period 4 - Atomic number: 35 - Classification: Nonmetal (halogen)

(g) Arsenic

- Chemical symbol: As - Located in the periodic table: Group 15, Period 4 - Atomic number: 33 - Classification: Metalloid

Key concepts

Chemical Symbols

Chemical symbols are shorthand notations used to represent elements in the periodic table. These symbols are usually one or two letters long, with the first letter always capitalized. For example:

• Chromium is represented by "Cr"
• Helium is abbreviated as "He"
• Phosphorus uses "P"

This system allows scientists and students alike to communicate efficiently about chemical elements. Each symbol is unique to its element, thereby preventing confusion. It's essential to get familiar with these symbols to read and understand the periodic table effectively.

Atomic Number

The atomic number of an element is a fundamental property. It tells us the number of protons found in the nucleus of one atom of the element. This number is key to locating an element's position on the periodic table.

• An atomic number of 24 corresponds to chromium
• With an atomic number of 2, helium is easy to find
• Phosphorus has an atomic number of 15

Knowing the atomic number also helps to determine an element’s identity and its place within the periodic table’s structure. It guides us in understanding how elements relate to each other chemically.

Element Classification

The classification of elements refers to their categorization into metals, nonmetals, and metalloids. This classification plays a vital role in predicting an element's properties and its behavior in reactions.

• Metals like chromium, zinc, and magnesium are typically shiny, conduct electricity, and are malleable.
• Nonmetals such as helium, phosphorus, and bromine lack metallic properties and are varied in their states at room temperature.
• Arsenic being a metalloid exhibits mixture properties found in both metals and nonmetals.

This classification helps scientists determine the practicality and potential applications of an element in different fields.