Briefly discuss the properties of the s block elements and explain why we say the periodic table has opposing factors?
The s block elements in the periodic table are the group 1 and group 2 elements, which include hydrogen, lithium, sodium, potassium, etc. These elements have similar characteristics as they have their outermost electron(s) in the s orbital.
Properties of s block elements:
1. Atomic size: The atomic size tends to increase as you move down the group. This is because the number of electron shells or energy levels increases, resulting in increased shielding effect and overall atomic size.
2. Ionization energy: The ionization energy, which is the energy required to remove an electron from an atom, tends to decrease down the group. This is due to the increased distance between the outermost electron and the nucleus, making it easier to remove the electron.
3. Reactivity: The s block elements are highly reactive metals. Group 1 elements (alkali metals) are the most reactive metals as they have a single outermost electron that is easily lost, resulting in the formation of positively charged ions. Group 2 elements (alkaline earth metals) are also reactive but less so compared to alkali metals.
4. Electronegativity: The s block elements have low electronegativity values. Electronegativity is a measure of an atom's ability to attract electrons towards itself. Since the s block elements have a tendency to lose electrons, they do not hold electrons tightly, resulting in low electronegativity.
The periodic table can be described as having opposing factors because as you move across a period (horizontal row), there is a gradual change in properties due to certain opposing factors. For example:
1. Atomic size: The atomic size tends to decrease as you move across a period. This is due to increased nuclear charge, which attracts the electrons more strongly, thereby reducing the atomic size.
2. Ionization energy: The ionization energy generally increases as you move across a period. This is because the electrons are held more tightly due to the stronger nuclear charge, making it more difficult to remove an electron.
3. Electronegativity: Electronegativity tends to increase across a period. As the atomic size decreases and nuclear charge increases, the atom's ability to attract electrons towards itself also increases.
Thus, the periodic table can be seen as a balance between opposing factors such as atomic size, ionization energy, and electronegativity, which change gradually across a period and within a group.