28) State any three characteristics of periods. Explain with examples
Answers
Answer:
ANSWER
There are 7 periods and 18 groups in the modern periodic table.
1. On moving from left to right in a periodic table, the metallic character of elements decreases.
Metals have a tendency to lose electrons. In a period, atomic size decreases so it becomes difficult to remove the electrons of the outermost shell.
2. On moving from top to bottom in a periodic table, the metallic character of element increases.
As we move down the group, atomic size increases so the electron of the outermost shell is easy to remove and hence metallic character of the element increases.
3. All period three elements occur in nature and have at least one stable isotope. All but the noble gas argon are essential to basic geology and biology.
Sodium (Na) is an alkali metal. It is present in Earth's oceans in large quantities in the form of sodium chloride (table salt).
Magnesium (Mg) is an alkaline earth metal. Magnesium ions are found in chlorophyll.
Aluminium (Al) is a post-transition metal. It is the most abundant metal in the Earth's crust.
Silicon (Si) is a metalloid. It is a semiconductor, making it the principal component in many integrated circuits. Silicon dioxide is the principal constituent of sand. As Carbon is to Biology, Silicon is to Geology.
Phosphorus (P) is a nonmetal essential to DNA. It is highly reactive, and as such is never found in nature as a free element.
Sulfur (S) is a nonmetal. It is found in two amino acids: cysteine and methionine.
Chlorine (Cl) is a halogen. It is used as a disinfectant, especially in swimming pools.
Argon (Ar) is a noble gas, making it almost entirely nonreactive. Incandescent lamps are often filled with noble gases such as argon in order to preserve the filaments at high temperatures.
What are the characteristics of periods?
A period in the periodic table is a row of chemical elements. All elements in a row have the same number of electron shells. Each next element in a period has one more proton and is less metallic than its predecessor.
What are the main characteristics of periods and groups?
The horizontal rows on the periodic table are called periods. So, in these groups, the reactivity decreases as we go from top to bottom. Valence electrons, valency, atomic size, ionization energy, metallic character, electron-positivity, electron-negativity and reactivity are the characteristics of groups.
The third period elements are called typical elements or representative elements because they represent the properties of their own group without anomalies. The third period consists of eight elements which are: sodium, magnesium, aluminium, silicon, phosphorus, sulfur, chlorine, and argon.