File Name: periodic table properties and trends .zip
- Grafton High School
- Periodic Classification of Elements : Trends in Modern Periodic Table
- Periodic trends
The Periodic Table is called this not just because it is a table of the elements, but because it is arranged to reflect the periodic trends of the elements. Atomic radius is half the distance between two identical atoms touching each other. As you move across the periodic table from right to left, each element contains one more electron and one more proton. The electrons form shells and are attracted strongly to the positive charge in the nucleus, pulling the shells closer to the center and effectively making the atom smaller with the addition of each proton. As you move down the periodic table, the valence of the the atom remains the same, but there are more filled electron shells between the outer electrons and the positive nucleus.
Grafton High School
Periodic trends are specific patterns that are present in the periodic table that illustrate different aspects of a certain element, including its size and its electronic properties. Major periodic trends include: electronegativity , ionization energy , electron affinity , atomic radius , melting point, and metallic character.
Periodic trends, arising from the arrangement of the periodic table, provide chemists with an invaluable tool to quickly predict an element's properties. These trends exist because of the similar atomic structure of the elements within their respective group families or periods, and because of the periodic nature of the elements.
Electronegativity can be understood as a chemical property describing an atom's ability to attract and bind with electrons. Because electronegativity is a qualitative property, there is no standardized method for calculating electronegativity. However, the most common scale for quantifying electronegativity is the Pauling scale Table A2 , named after the chemist Linus Pauling.
The numbers assigned by the Pauling scale are dimensionless due to the qualitative nature of electronegativity. Electronegativity values for each element can be found on certain periodic tables. An example is provided below. Electronegativity measures an atom's tendency to attract and form bonds with electrons.
This property exists due to the electronic configuration of atoms. Most atoms follow the octet rule having the valence, or outer, shell comprise of 8 electrons. Because elements on the left side of the periodic table have less than a half-full valence shell, the energy required to gain electrons is significantly higher compared with the energy required to lose electrons. As a result, the elements on the left side of the periodic table generally lose electrons when forming bonds.
Conversely, elements on the right side of the periodic table are more energy-efficient in gaining electrons to create a complete valence shell of 8 electrons.
The nature of electronegativity is effectively described thus: the more inclined an atom is to gain electrons, the more likely that atom will pull electrons toward itself. According to these two general trends, the most electronegative element is fluorine , with 3. Ionization energy is the energy required to remove an electron from a neutral atom in its gaseous phase. Conceptually, ionization energy is the opposite of electronegativity.
The lower this energy is, the more readily the atom becomes a cation. Therefore, the higher this energy is, the more unlikely it is the atom becomes a cation. Generally, elements on the right side of the periodic table have a higher ionization energy because their valence shell is nearly filled.
Elements on the left side of the periodic table have low ionization energies because of their willingness to lose electrons and become cations.
Thus, ionization energy increases from left to right on the periodic table. Another factor that affects ionization energy is electron shielding. Electron shielding describes the ability of an atom's inner electrons to shield its positively-charged nucleus from its valence electrons.
When moving to the right of a period, the number of electrons increases and the strength of shielding increases. As a result, it is easier for valence shell electrons to ionize, and thus the ionization energy decreases down a group. Electron shielding is also known as screening.
Some elements have several ionization energies; these varying energies are referred to as the first ionization energy, the second ionization energy, third ionization energy, etc. The first ionization energy is the energy requiredto remove the outermost, or highest, energy electron, the second ionization energy is the energy required to remove any subsequent high-energy electron from a gaseous cation, etc. Below are the chemical equations describing the first and second ionization energies:.
Generally, any subsequent ionization energies 2nd, 3rd, etc. Ionization energies decrease as atomic radii increase. The relationship is given by the following equation:. As the name suggests, electron affinity is the ability of an atom to accept an electron. Unlike electronegativity, electron affinity is a quantitative measurement of the energy change that occurs when an electron is added to a neutral gas atom.
The more negative the electron affinity value, the higher an atom's affinity for electrons. Electron affinity generally decreases down a group of elements because each atom is larger than the atom above it this is the atomic radius trend, discussed below. This means that an added electron is further away from the atom's nucleus compared with its position in the smaller atom.
With a larger distance between the negatively-charged electron and the positively-charged nucleus, the force of attraction is relatively weaker.
Therefore, electron affinity decreases. Moving from left to right across a period, atoms become smaller as the forces of attraction become stronger.
This causes the electron to move closer to the nucleus, thus increasing the electron affinity from left to right across a period.
The atomic radius is one-half the distance between the nuclei of two atoms just like a radius is half the diameter of a circle. However, this idea is complicated by the fact that not all atoms are normally bound together in the same way. Some are bound by covalent bonds in molecules, some are attracted to each other in ionic crystals, and others are held in metallic crystals.
Nevertheless, it is possible for a vast majority of elements to form covalent molecules in which two like atoms are held together by a single covalent bond. The covalent radii of these molecules are often referred to as atomic radii. This distance is measured in picometers. Atomic radius patterns are observed throughout the periodic table. Atomic size gradually decreases from left to right across a period of elements.
This is because, within a period or family of elements, all electrons are added to the same shell. However, at the same time, protons are being added to the nucleus, making it more positively charged. The effect of increasing proton number is greater than that of the increasing electron number; therefore, there is a greater nuclear attraction.
This means that the nucleus attracts the electrons more strongly, pulling the atom's shell closer to the nucleus. The valence electrons are held closer towards the nucleus of the atom. As a result, the atomic radius decreases. D own a group, atomic radius increases. The valence electrons occupy higher levels due to the increasing quantum number n.
Electron shielding prevents these outer electrons from being attracted to the nucleus; thus, they are loosely held, and the resulting atomic radius is large. The melting points is the amount of energy required to break a bond s to change the solid phase of a substance to a liquid. Generally, the stronger the bond between the atoms of an element, the more energy required to break that bond. Because temperature is directly proportional to energy, a high bond dissociation energy correlates to a high temperature.
Melting points are varied and do not generally form a distinguishable trend across the periodic table. The metallic character of an element can be defined as how readily an atom can lose an electron. From right to left across a period, metallic character increases because the attraction between valence electron and the nucleus is weaker, enabling an easier loss of electrons.
Metallic character increases as you move down a group because the atomic size is increasing. When the atomic size increases, the outer shells are farther away. The principal quantum number increases and average electron density moves farther from nucleus. The electrons of the valence shell have less attraction to the nucleus and, as a result, can lose electrons more readily.
This causes an increase in metallic character. Another easier way to remember the trend of metallic character is that moving left and down toward the bottom-left corner of the periodic table, metallic character increases toward Groups 1 and 2, or the alkali and alkaline earth metal groups.
Likewise, moving up and to the right to the upper-right corner of the periodic table, metallic character decreases because you are passing by to the right side of the staircase, which indicate the nonmetals. These include the Group 8, the noble gases , and other common gases such as oxygen and nitrogen. Based on the periodic trends for ionization energy, which element has the highest ionization energy? Answer: C. Helium He Explanation: Helium He has the highest ionization energy because, like other noble gases, helium's valence shell is full.
Therefore, helium is stable and does not readily lose or gain electrons. Answer: A. True Explanation: Atomic radius increases from right to left on the periodic table. Therefore, nitrogen is larger than oxygen. Answer: Lead Pb Explanation: Lead and tin share the same column. Metallic character increases down a column. Lead is under tin, so lead has more metallic character.
Answer: Bromine Br Explanation: In non-metals, melting point increases down a column. Because chlorine and bromine share the same column, bromine possesses the higher melting point.
Answer: Sulfur S Explanation: Note that sulfur and selenium share the same column. Electronegativity increases up a column. This indicates that sulfur is more electronegative than selenium. Answer: Most noble gases have full valence shells. Explanation: Because of their full valence electron shell, the noble gases are extremely stable and do not readily lose or gain electrons. Explanation: The electrons above a closed shell are shielded by the closed shell.
S has 6 electrons above a closed shell, so each one feels the pull of 6 protons in the nucleus. Oxygen O Explanation: Periodic trends indicate that atomic radius increases up a group and from left to right across a period. Therefore, oxygen has a smaller atomic radius sulfur. Answer: B. False Explanation: The reasoning behind this lies in the fact that a metal usually loses an electron in becoming an ion while a non-metal gains an electron.
Periodic Classification of Elements : Trends in Modern Periodic Table
Trends in Modern Periodic Table. The term periodic properties in elements, refers to the properties that recur at regular intervals. The trend of recurrence of properties is called periodicity. Important periodic properties are:. Atomic radius is the distance from the centre of the nucleus to the valence electron in an energy level.
Periodic trends are specific patterns that are present in the periodic table that illustrate different aspects of a certain element, including its size and its electronic properties. Major periodic trends include: electronegativity , ionization energy , electron affinity , atomic radius , melting point, and metallic character. Periodic trends, arising from the arrangement of the periodic table, provide chemists with an invaluable tool to quickly predict an element's properties. These trends exist because of the similar atomic structure of the elements within their respective group families or periods, and because of the periodic nature of the elements. Electronegativity can be understood as a chemical property describing an atom's ability to attract and bind with electrons.
Periodic trends are specific patterns in the properties of chemical elements that are revealed in the periodic table of elements. Major periodic trends include electronegativity , ionization energy , electron affinity , atomic radii , ionic radius , metallic character , and chemical reactivity. Periodic trends arise from the changes in the atomic structure of the chemical elements within their respective periods horizontal rows and groups in the periodic table. These laws enable the chemical elements to be organized in the periodic table based on their atomic structures and properties. Due to the periodic trends, the unknown properties of any element can be partially known.
This table prints up great from the PDF file. The first two used a combination of Roman numerals and letters. Moving from the far left to the right on the periodic table, main-group elements tend to form cations with a charge equal to the group number.
Classification of Elements and Periodicity in Properties is the root concept of Chemistry. Thus, it becomes very important that you are crystal clear with all the concepts involved. Periodic table helps in the systematic study of most of the elements found in nature.
The periodic table of elements has a total of entries. Elements are arranged in a series of rows periods in order of atomic number so that those with similar properties appear in vertical columns. Elements in the same period have the same number of electron shells; moving across a period so progressing from group to group , elements gain electrons and protons and become less metallic. This arrangement reflects the periodic recurrence of similar properties as the atomic number increases. For example, the alkali metals lie in one group Group 1 and share similar properties, such as high reactivity and the tendency to lose one electron to arrive at a noble-gas electron configuration.