Elements in the periodic table are often divided into four categories: elements of the main group, 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 non-metals in six columns on the far right. These transition metals are metal elements that act as a kind of bridge or transition between parts of the sides of the periodic table.
What it is
Of all the groups of chemical elements, transition metals may be the most difficult to identify, because there are different opinions as to what exactly should be included there. According to one of the definitions, they include any substances with a partially filled d-electron subshell (habitat). This description refers to groups 3 through 12 in the periodic table, although f-block elements (lanthanides and actinides below the main part of the periodic table) are also transition metals.
Their name is associated with the name of the English chemist Charles Bury, who used it in 1921.
Place in the periodic table
Transitional are all metals of the series located in groups from IB to VIIIB of the periodic table:
- from the 21st (scandium) to the 29th (copper);
- from the 39th (yttrium) to the 47th (silver);
- from the 57th (lanthanum) to the 79th (gold);
- from the 89th (sea anemone) to the 112th (Copernicus).
The last group includes lanthanides and actinides (the so -called f-elements, which are their special group, all the rest belong to d-elements).
Transition Metals: List
The list of these elements is presented:
- scandium;
- titanium;
- vanadium;
- chrome;
- manganese;
- iron;
- cobalt;
- nickel;
- copper;
- zinc
- yttrium;
- zirconium;
- niobium;
- molybdenum;
- technetium;
- ruthenium;
- rhodium;
- palladium;
- silver
- cadmium;
- hafnium;
- tantalum;
- tungsten;
- rhenium;
- osmium
- iridium;
- platinum;
- gold
- mercury;
- reserfody;
- tannin;
- seaborgium;
- boron;
- hassiy;
- meitnerium;
- darmstadtiy;
- X-ray
- ununbium.
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:
- sea anemone;
- thorium;
- protactinium;
- uranium;
- neptunium;
- plutonium;
- americium;
- Curie
- Berkeley
- california;
- einsteinemia;
- Fermium
- Mendelevium
- nobelium;
- lawrence.
Features
During the formation of compounds, metal atoms can be used as valence s and p electrons, and d electrons. Therefore, d-elements in most cases are characterized by variable valency, in contrast to 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. When moving from left to right on the periodic table, the five d-orbitals become more full. Their electrons are loosely coupled, which contributes to the high conductivity and compliance of the transition elements. They also have a low ionization energy (it is required when an electron is removed from a free atom).
Chemical properties
Transition metals exhibit a wide range 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 conductivity and thermal conductivity. They are malleable. Usually form paramagnetic compounds due to unpaired d-electrons. They also have a high catalytic activity.
It should also be noted that there is some controversy about the classification of elements on the border 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
The disagreement as to whether they should be classified as belonging to the main group or transition metals suggests that the differences between these categories are not clear. There is a certain similarity between them: they look like metals, they are malleable and ductile, they conduct heat and electricity and form positive ions. The fact that the two best conductors of electricity are transition metal (copper) and an element belonging to the main group (aluminum) shows the degree to which the physical properties of the elements of these two groups overlap.
Comparative characteristics
There are also differences between base and transition metals. For example, the latter are more electronegative than representatives of the main group. Therefore, they are more likely to form covalent compounds.
Another difference between the metals of the main group and the transition metals can be seen in the formulas of the compounds that they form. The former tend to form salts (such as NaCl, Mg 3 N 2 and CaS), in which only negative ions are enough to balance the charge on the positive ions. Transition metals form similar compounds, such as FeCl 3 , HgI 2 or Cd (OH) 2 . However, they more often than the metals of the main group form complexes, such as FeCl4-, HgI 4 2- and Cd () 4 2-, which have 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.