Respuesta :
H - hydrogen
Li - lithium
Na - sodium
K - potassium
Rb - rubidium
Cs - cesium
Fr - francium
These elements are in the first main group because they only have one valence electron, which is located in an s orbital.
The atomic size increases from H to Fr.
The ordinal number increases from H to Fr.
The mass number increases from H to Fr.
The reactivity increases from H to Fr.
The melting point drops from Li to Fr.
The boiling point drops from Li to Fr.
Answer:
Lithium
Sodium
Potassium
Rubidium
Caesium
2. They readily react with water to form an alkaline solution of the hydroxide e.g. sodium produced the well known alkali sodium hydroxide.
Explanation:
Lithium; Li
Atomic size: 182 pm
Atomic number: 3
Mass number: 6.941 u
Reactivity: Lithium reacts with water normally, but with less vigor than other metals used in the alkali solution.
Boiling: 2,426 °F
Melting: 357 °F
Sodium; Na
Atomic size: 227 pm
Atomic number: 11
Mass number: 22.989769 u
Reactivity: Sodium metal reacts rapidly with water to form a colourless basic solution of NaOH and H2. The reaction continues even when the solution becomes basic.
Boiling: 1,621 °F
Melting: 208 °F
Potassium; K
Atomic size: 280 pm
Atomic number: 19
Mass number: 39.0983 u
Reactivity: The conflagration occurs because the combination of potassium and water creates potassium hydroxide (KOH) and hydrogen gas, as well as heat.
Boiling: 1,398 °F
Melting: 146.3°F
Rubidium; Rb
Atomic size: 290 pm
Atomic number: 37
Mass number: 85.4678 u
Reactivity: rubidium metal reacts violently with water. This reaction is usually vigorous enough to ignite the hydrogen gas it produces.
Boiling: 1,270 ° F
Melting: 102.7°F
Caesium; Cs
Atomic size: 343 pm
Atomic number: 55
Mass number: 132.90545 u
Reactivity: Caesium metal is highly reactive and very pyrophoric. It ignites spontaneously in air, and reacts explosively with water even at low temperatures, more so than the other alkali metals (first group of the periodic table).
Boiling: 1,240 ° F
Melting: 83.19°F
