Question

Refer to the periodic table and indicate the physical state for each of the following elements at \(25^{\circ} \mathrm{C}\) and normal pressure: (a) hydrogen (b) titanium (c) fluorine (d) bromine

Short answer

(a) Gas, (b) Solid, (c) Gas, (d) Liquid.

Step-by-step solution

Identify hydrogen's physical state

Hydrogen is the first element in the periodic table. At \(25^{\circ} \mathrm{C}\) and normal pressure, hydrogen exists as a diatomic gas \(H_2\). So, the physical state of hydrogen is gaseous.

Determine titanium's state

Titanium is a transition metal, found in the fourth period and group 4 of the periodic table. At \(25^{\circ} \mathrm{C}\), titanium is a solid metal.

Establish fluorine's state

Fluorine is a halogen located in group 17 (or VIIA). At \(25^{\circ} \mathrm{C}\), fluorine exists as a diatomic molecule \(F_2\) and is a gas.

Identify bromine's physical state

Bromine, another halogen found in group 17, is unique for being a liquid at \(25^{\circ} \mathrm{C}\) and normal pressure, existing as \(Br_2\).

Key concepts

Physical State of Elements

When exploring the physical state of elements at room temperature, it's intriguing to see how varied the states can be. Depending on their atomic structure and interactions between their particles, elements could solidify into metals, wisp into gases, or flow as liquids.
At a common reference point of 25°C (77°F), which is around room temperature, and under normal atmospheric pressure, most metals like titanium are solids due to tightly packed atoms that hold together strongly. Even within such similar conditions, elements can surprise us with their physical diversity, indicative of the wonders of chemistry.

Diatomic Molecules

A diatomic molecule is composed of two atoms bonded together. Surprisingly, many nonmetals exist naturally as diatomic molecules, particularly in gaseous states. For instance, hydrogen forms the molecule hydrogen gas, or \(H_2\), while fluorine forms fluorine gas, or \(F_2\).

• These diatomic molecules exist because these elements achieve greater stability together than alone.
  Their bonds hold energy and dictate their physical state at normal conditions.
• Gases consist of these molecules floating freely with weak attractions between particles, explaining their gaseous form.

This brief look into diatomic molecules helps us understand why certain elements embrace becoming a pair.

Transition Metals

Transition metals are elements laying in the central d-block of the periodic table, characterized by variable oxidation states and a propensity to facilitate electron transfers. One such example is titanium, residing solidly in the metallic class, under common room conditions.

• They possess tightly bound electron clouds that allow metals like titanium to form solid structures.
• Their malleable and ductile nature comes from the flexibility offered by delocalized electrons.

This group operates as workhorses of the periodic table, bridging a gap between simple metals and more reactive classes like the nonmetals.

Halogens

Halogens, from the Greek roots meaning "salt-formers," make up group 17 on the periodic table and include elements such as fluorine and bromine. Unique to this group is their diversity in physical states, spanning gases like fluorine ( F_2 ), to liquids like bromine ( Br_2 ) at room temperature.

• Fluorine, the most reactive, is a pale yellow gas, taking no prisoners in chemical reactions.
• Bromine, meanwhile, offers an interesting twist as a dark, reddish-brown liquid at room conditions.

The halogens are fascinating not only for their bold reactivity but also for their growing diversity in how we encounter them physically.