1. Atomic radius
1 Factors that affect the size of the atomic radius.
2 The law of gradual change of atomic radius.
2. The ionization energy of an element
1 element first ionization energy.
1) Concept: The minimum energy required for a gaseous electrically neutral ground state atom to lose an electron and convert into a gaseous ground state positive ion is called the first ionization energy, symbol: i1.
2) The law of change in the first ionization energy of the element.
The first ionization energy of the first element of each cycle is the smallest, and the first ionization energy of the last element is the largest, that is, in general, with the increase of the number of nuclear charges, the first ionization energy of the element shows an increasing trend;
In the same family, the first ionization energy gradually decreases from top to bottom.
Thinking about the factors that affect ionization energy.
Generally speaking, elements in the same period have the same number of electron shells, and the number of nuclear charges increases from left to right, the radius of the atom decreases, and the attraction of the nucleus to the outermost electron increases, so the more right the element is less likely to lose electrons, and the greater the ionization energy.
The number of electron layers of the same main group element is different, the number of electrons in the outermost shell is the same, and the gradual increase of the atomic radius plays a major role, so the larger the radius, the smaller the attraction of the nucleus to the outermost electron, the easier it is to lose electrons, and the smaller the ionization energy.
3) Significance: It can measure the difficulty of the atom of the element to lose an electron, the smaller the ionization energy, the easier it is for the atom of the element to lose an electron in the gaseous state.
Infocard] Influencing Factors and Special Cases of Ionization Energy.
Understanding the Application In the figure below, the curve of the first ionization energy of the element of the third period is plotted.
2 Stepwise ionization energy.
1) Meaning: The minimum energy required for a gaseous ground state divalent cation to lose one more electron to become a gaseous ground state divalent positive ion is called the second ionization energy, the third ionization energy, and the first.
Fourth, the fifth ionization energy and so on.
A deep understanding of the ionization energy of sodium, magnesium, and aluminum that gradually lose electrons.
Why is the stepwise ionization energy of atoms getting bigger and bigger?
Hint Since the atom loses one electron and becomes a +1 valence cation, the radius becomes smaller, the number of nuclear charges does not change but the number of electrons decreases, the attraction of the nucleus to the outer electrons is enhanced, making it more difficult for the second electron to lose than the first electron, and it takes more energy to lose the second electron than the first electron.
What is the relationship between these data and the valency of sodium, magnesium and aluminum?
Hint If the ionization energy jumps between in and in 1, the atoms of the element are easy to form n-valence ions, and the highest valency of the main group elements is n-valence.
The ionization energy of the element atom gradually increases and a mutation occurs, indicating what are the characteristics of the electron configuration outside the nucleus
Hint Illustrates that electrons outside the nucleus are arranged in layers.
The value of ionization energy mainly depends on the number of nuclear charges, the radius of the atom and the electronic configuration of the atom.
3 Applications of ionization energy.
1) Compare the strength of the metallicity of the element: In general, the smaller the first ionization energy of the element, the stronger the metallicity of the element.
2) Determine the electron configuration outside the nucleus of the element atom: Since the electrons are arranged in layers, the inner electrons are more difficult to lose than the outer electrons, so the ionization energy of the element will undergo a sudden jump.
3) Determine the valency of the element: if.
That is, if the ionization energy jumps between in and in 1, the atoms of the element are prone to form n-valent ions.
3. Electronegativity
1 Concepts and Meanings.
1) Bonding electrons: The electrons in an atom that are used to form chemical bonds when elements are combined with each other.
2) Electronegativity: It is used to describe the amount of attraction of atomic pairs bonded electrons of different elements. The more electronegative the atom, the greater the attraction to the bonding electrons.
3) The standard of electronegativity: the electronegativity of fluorine is 40 and lithium have an electronegativity of 10 as a relative criterion.
2 The law of gradual change.
1) In the same period, from left to right, the electronegativity of the element gradually increases.
2) In the same main group, from top to bottom, the electronegativity of the elements gradually decreases.
3 Applications. 1) Judge the strength of the metallic and non-metallic properties of the elements.
2) Determine the valency of the element.
Elements with low electronegativity values have a weak ability to attract electrons in the compound, and the valency of the element is positive.
Elements with high electronegativity values have a strong ability to attract electrons in compounds, and the valency of the elements is negative.