Question

Identify the elements that correspond to the following atomic numbers. Label each as either a noble gas, a halogen, an alkali metal, an alkaline earth metal, a transition metal, a lanthanide metal, or an actinide metal. a. 17 b. 4 c. 63 d. 72 e. 2 f. 92 g. 55

Short answer

a. Chlorine (Cl) - Halogen b. Beryllium (Be) - Alkaline Earth Metal c. Europium (Eu) - Lanthanide Metal d. Hafnium (Hf) - Transition Metal e. Helium (He) - Noble Gas f. Uranium (U) - Actinide Metal g. Cesium (Cs) - Alkali Metal

Step-by-step solution

a. Identifying element with atomic number 17 and its classification

The element with atomic number 17 is Chlorine (Cl). Looking at the Periodic Table, we can see that Chlorine belongs to Group 17 and is a non-metal. Elements in Group 17 are called halogens. So, Chlorine (Cl) is a halogen.

b. Identifying element with atomic number 4 and its classification

The element with atomic number 4 is Beryllium (Be). Beryllium is in Group 2 and is a metal. Members of Group 2 are called alkaline earth metals. So, Beryllium (Be) is an alkaline earth metal.

c. Identifying element with atomic number 63 and its classification

The element with atomic number 63 is Europium (Eu). Europium is part of the series of elements called lanthanides. Specifically, it is in the f-block of the Periodic Table, where the lanthanides are placed. So, Europium (Eu) is a lanthanide metal.

d. Identifying element with atomic number 72 and its classification

The element with atomic number 72 is Hafnium (Hf). Hafnium is in Group 4 and is a metal. The elements found in groups 3-12 are known as transition metals. So, Hafnium (Hf) is a transition metal.

e. Identifying element with atomic number 2 and its classification

The element with atomic number 2 is Helium (He). Helium is in Group 18 and is a non-metal. Elements in Group 18 are called noble gases. So, Helium (He) is a noble gas.

f. Identifying element with atomic number 92 and its classification

The element with atomic number 92 is Uranium (U). Uranium is part of the series of elements called actinides. Specifically, it is in the f-block of the Periodic Table, where the actinide series is placed. So, Uranium (U) is an actinide metal.

g. Identifying element with atomic number 55 and its classification

The element with atomic number 55 is Cesium (Cs). Cesium is in Group 1 and is a metal. Members of Group 1 are called alkali metals. So, Cesium (Cs) is an alkali metal.

Key concepts

Atomic Number

The atomic number of an element is a fundamental property in chemistry. It represents the number of protons found in the nucleus of an atom of that element. This number is unique for each element and determines its identity.
For example, hydrogen has an atomic number of 1, meaning it has one proton in its nucleus. Similarly, carbon, which is another element, has an atomic number of 6, reflecting its six protons.

The atomic number is crucial as it dictates the element's position in the periodic table. It also influences many chemical and physical properties of the element, including reactivity and bonding behavior.

Element Classification

Element classification is a system that organizes elements into specific categories based on their properties. This classification helps chemists and students understand and predict the behavior of elements.

The periodic table is primarily used for this classification, and elements are typically grouped into:

• Metals - Good conductors of heat and electricity, often malleable and shiny.
• Non-metals - Poor conductors of heat and electricity, often brittle in solid form.
• Metalloids - Have properties of both metals and non-metals.

Additionally, elements can be placed into more specific families, such as alkali metals, alkaline earth metals, transition metals, and more, each group sharing certain chemical properties.

Halogens

Halogens are a group of elements found in Group 17 of the periodic table. This group includes fluorine, chlorine, bromine, iodine, and astatine.

Here's what makes halogens special:

• They are highly reactive, particularly with alkali and alkaline earth metals, due to having seven valence electrons, which makes them eager to gain one more to achieve a full outer electron shell.
• Halogens are efficient at forming salts when combined with metals, for example, sodium chloride (table salt).
• The chemical and physical properties of halogens change predictably as you move down the group, such as increasing atomic size and decreasing volatility.

Noble Gases

Noble gases are located in Group 18 of the periodic table. This group includes helium, neon, argon, krypton, xenon, and radon.

They have several defining properties:

• Noble gases are known for being inert or non-reactive due to having full valence electron shells, which makes them very stable.
• This non-reactivity is why they rarely form compounds with other elements.
• They are colorless, odorless, and tasteless in standard conditions, making them difficult to detect.

Despite their low reactivity, noble gases have essential applications, such as in lighting (neon lights) or helium-filled balloons.

Transition Metals

Transition metals are found in the central block of the periodic table, covering Groups 3 through 12. They include elements like iron, copper, and gold.

These metals have unique features:

• They have the ability to form compounds with a wide variety of oxidation states, which makes them versatile in reactions.
• Transition metals often have high melting and boiling points due to their complex electron structures.
• They are typically excellent conductors of electricity and have vibrant colors owing to the d-electrons' ability to absorb and emit light at various wavelengths.

Their chemical and physical properties make them invaluable in industry and technology, from constructing structures to being catalysts in chemical reactions.