Elements in the periodic table are often divided into four categories: main group elements, transition metals, lanthanides, and actinides. The main elements of the group include active metals in two columns on the far left of the periodic table and metals, semimetals and nonmetals in six columns on the far right. These transition metals are metallic elements that act as a kind of bridge or transition between the parts of the sides of the periodic table.
What is this
Of all the chemical element groups, the transition metals can be the most difficult to identify because there are different opinions as to exactly what should be included. According to one of the definitions, they include any substances with a partially filled d-electron subshell (inhabitant). This description applies to groups 3 to12th in the periodic table, although the f-block elements (the lanthanides and actinides below the bulk of the periodic table) are also transition metals.
Their name comes from the English chemist Charles Bury, who used it in 1921.
Place in the periodic table
Transition metals are all series located in groups from IB to VIIIB of the periodic table:
- from 21st (scandium) to 29th (copper);
- from 39th (yttrium) to 47th (silver);
- from 57th (lanthanum) to 79th (gold);
- from 89th (actinium) to 112th (Copernicus).
The last group includes the lanthanides and actinides (the so-called f-elements, which are their special group, all the rest are d-elements).
Transition metals list
The list of these elements is presented:
- scandium;
- titanium;
- vanadium;
- chrome;
- manganese;
- iron;
- cob alt;
- nickel;
- copper;
- zinc;
- yttrium;
- zirconium;
- niobium;
- molybdenum;
- technetium;
- ruthenium;
- rhodium;
- palladium;
- silver;
- cadmium;
- hafnium;
- tantalum;
- tungsten;
- rhenium;
- osmium;
- iridium;
- platinum;
- gold;
- mercury;
- reserfodium;
- dubnium;
- seaborgium;
- borium;
- Hassiem;
- meitnerium;
- Darmstadt;
- X-ray;
- ununbiem.
The lanthanide group is represented by:
- lanthanum;
- cerium;
- praseodymium;
- neodymium;
- promethium;
- samarium;
- europium;
- gadolinium;
- terbium;
- dysprosium;
- holmium;
- erbium;
- thulium;
- ytterbium;
- lutetium.
Actinides are represented by:
- actinium;
- thorium;
- protactinium;
- uranium;
- neptunium;
- plutonium;
- americium;
- curium;
- berkelium;
- californium;
- einsteinium;
- fermiem;
- mendelevium;
- nobel;
- lawrencium.
Features
In the process of formation of compounds, metal atoms can be used as valence s- and p-electrons, as well as d-electrons. Therefore, d-elements in most cases are characterized by variable valence, in contrast to the elements of the main subgroups. This property determines their ability to form complex compounds.
The presence of certain properties determines the name of these elements. All transition metals of the series are solid with high melting and boiling points. As you move from left to right across the periodic table, the five d-orbitals become more filled. Their electrons are weakly bound, which contributes to high electrical conductivity and compliance.transition elements. They also have a low ionization energy (it is required when an electron moves away from a free atom).
Chemical properties
Transition metals exhibit a wide variety of oxidation states or positively charged forms. In turn, they allow transition elements to form many different ionic and partially ionic compounds. The formation of complexes leads to the splitting of d-orbitals into two energy sublevels, which allows many of them to absorb certain frequencies of light. Thus, characteristic colored solutions and compounds are formed. These reactions sometimes enhance the relatively low solubility of certain compounds.
Transition metals are characterized by high electrical and thermal conductivity. They are malleable. Usually form paramagnetic compounds due to unpaired d-electrons. They also have high catalytic activity.
It should also be noted that there is some controversy about the classification of elements at the boundary between the main group and transition metal elements on the right side of the table. These elements are zinc (Zn), cadmium (Cd), and mercury (Hg).
Systematization problems
Controversy over whether to classify them as main group or transition metals suggests that the distinctions between these categories are not clear. There are certain similarities between them: they look like metals, they are malleable andplastic, they conduct heat and electricity and form positive ions. The fact that the two best conductors of electricity are a transition metal (copper) and a main group element (aluminum) shows the degree to which the physical properties of the elements of the two groups overlap.
Comparative characteristics
There are also differences between base and transition metals. For example, the latter are more electronegative than the representatives of the main group. Therefore, they are more likely to form covalent bonds.
Another difference between main group metals and transition metals can be seen in the formulas of the compounds they form. The former tend to form s alts (such as NaCl, Mg 3 N 2 and CaS) in which only the negative ions are sufficient to balance the charge on the positive ions. Transition metals form analogous compounds such as FeCl3, HgI2 or Cd (OH)2. However, they more often than main group metals form complexes such as FeCl4-, HgI42- and Cd (OH)42-, having an excess of negative ions.
Another difference between the main group and transition metal ions is the ease with which they form stable compounds with neutral molecules such as water or ammonia.
