Describe, in detail, the arrangement of the periodic table, and why it is sometimes referred to as the "chemists' calendar". Describe the rows and columns. What do they tell us about the elements in each row or column? What other trends are on the periodic table?

The periodic table is an arrangement of chemical elements based on increasing atomic numbers.

Explanation:

The periodic table is an arrangement of chemical elements in order of increasing atomic numbers. According to the modern periodic law, the properties of elements is a periodic function of their atomic numbers.

The periodic table is arranged in columns and rows. The columns are called groups of elements. All elements in the same group have the same number of electrons on their outermost shell hence they possess the same chemical behavior. Elements across a period have the same number of shells thus they have the same maximum excitation level.

There are important trends across the periodic table such as atomic radius, ionic radius, electro negativity, electron affinity, melting and boiling points, metallic properties etc. All these depend on an elements position in the periodic table. periodic properties of elements increase or decrease across the period or increase or decrease down the group as the case maybe.

Hence, just as one can easily read off the date and make predictions based on dates shown in a calendar, a chemist can read off the properties of elements and make predictions about the reactivity and physical properties of elements based on their relative position in the periodic table.

Gradual changes that occur down the group in the periodic table are called group trends and they usually very significant in discussing the properties of members of a group.

the equation that correctly represent the reaction for formation of ammonia is

n2+ 3h2 → 2nh3 (answer d)

1 mole of nitrogen gas (n2) react with 3 moles of hydrogen gas (h2) to form 2 moles of ammonia ( nh3). this is in a process known as haber process were iron is used as a catalyst and reaction take place that a higher temperature and pressure. the process is exothermic hence energy is released.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.