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  錒系元素皆為銀灰色有光澤的放射性金屬,半衰期隨著原子序的擴大而依次縮短。錒系元素的性質較軟,具有較高的密度及可塑性,在空氣中會失去光澤。與鑭系元素一樣,錒系元素的化學性質比較活潑,能形成錯合物及可溶於水的氯化物、硫酸鹽、硝酸鹽及高氯酸鹽等,至於它們的氫氧化物、氟化物、硫酸鹽及草酸鹽等則不溶於水。

  鐒(Lr)是否屬於錒系元素有爭論。最近的色譜分析顯示,鐒應屬於IIIB族,而非錒系。但為了方便敘述,現今仍習慣將其與錒系合稱。參見鑭系元素中關於鎦的地位的爭論。

  與同族的鈧、釔、鑭、錒原子半徑逐漸增大的規律恰恰相反,從釷到鐒則是逐漸減小。這種錒系元素的原子半徑和離子半徑隨原子序數的增加而逐漸減小的現象稱為錒系收縮。  錒系元素中,充填最初幾個元素的5f電子時,離子半徑收縮地比較明顯,但此現象後來趨於平緩,使得這些較重的錒系元素的離子半徑十分接近。因此錒系元素在化學性質上的差別隨著原子序數的增大而逐漸變小,以致逐個地分離錒系元素(尤其是重錒系元素)越來越困難。

  地殼中含量最豐富的錒系元素為釷和鈾,它們兩者具有很長的半衰期,放射性較微弱,因此能在地殼中以穩定的量存在。主要的含鈾礦物有釩酸鉀鈾礦和鈣鈾雲母等,而釷主要分佈在獨居石、方釷石和釷石等礦物中。大多數含釷礦物中皆含有鈾,反之亦然,且這些礦物中也都含有大量的鑭系元素。而鏷和錒主要分佈在各種鈾礦中,含量甚低。至於超鈾元素大多不存在於自然界中,必須透過粒子加速器人工合成,只有部分較輕的元素如錼和鈽等以痕量存在於鈾礦中。

  儘管部分錒系元素已在日常生活中得到了應用,例如煙霧偵測器中的鋂和煤氣網罩中的釷等,但錒系元素主要用於核武器,或當作核反應堆的燃料,例如鈾和鈽等。而原子序較大的重錒系元素由於製備的難度較高,且較不穩定,因此只用於學術研究,而沒有實際用途。  在核反應堆最重要的同位素是鈾-235。它被用於如核反應堆,且在天然鈾裡有0.72%的鈾-235。它強烈吸收熱中子,然後放出能量。鈾235核子吸收中子後,會裂變成2個較輕的核子和2至3顆中子,如:  Other promising actinide isotopes for nuclear power are thorium-232 and its product from the thorium fuel cycle, uranium-233.  Emission of neutrons during the fission of uranium is important not only for maintaining the nuclear chain reaction, but also for the synthesis of the heavier actinides. Uranium-239 converts via β-decay into plutonium-239, which, like uranium-235, is capable of spontaneous fission. The world's first nuclear reactors were built not for energy, but for producing plutonium-239 for nuclear weapons.  釷除了用作煤氣網罩的材料之外,也常和鎂、鋁等金屬做成合金,因為鎂釷合金不但堅固,還具有高熔點及高延展性,因此被廣泛用於航空工業和導彈的生產中。釷還有著良好的電子發射效能,可用作電子器件中的高效電子發射極。此外釷的半衰期很長,和鈾同位素的相對含量被廣泛用於估算包括恆星在內的各種物體的年齡(參見放射性定年法)。  鈽元素的主要用途是製造核武器,尤其是可以裂變的鈽-239。它的臨界質量是鈾-235的1/3。  Plutonium-238 is potentially more efficient isotope for nuclear reactors, since it has smaller critical mass than uranium-235, but it continues to release much thermal energy (0.56 W/g) by decay even when the fission chain reaction is stopped by control rods. Its application is limited by the high price (about US$1000/g). This isotope has been used in thermopiles and water distillation systems of some space satellites and stations. So Galileo and Apollo spacecraft (e.g. Apollo 14) had heaters powered by kilogram quantities of plutonium-238 oxide; this heat is also transformed into electricity with thermopiles. The decay of plutonium-238 produces relatively harmless alpha particles and is not accompanied by gamma-irradiation. Therefore, this isotope (~160 mg) is used as the energy source in heart pacemakers where it lasts about 5 times longer than conventional batteries.  錒-227是中子源。 Its high specific energy (14.5 W/g) and the possibility of obtaining significant quantities of thermally stable compounds are attractive for use in long-lasting thermoelectric generators for remote use. Ac is used as an indicator of radioactivity in chemical research, as it emits high-energy electrons (2.18 MeV) that can be easily detected. Ac-Ra mixtures are widely used as an intense gamma-source in industry and medicine.  Development of self-glowing actinide-doped materials with durable crystalline matrices is a new area of actinide utilization as the addition of alpha-emitting radionuclides to some glasses and crystals may confer luminescence.

  由於錒系元素皆具有放射性,對生物而言具有極高的毒性,過度暴露在它們散發出的輻射中會損害人體健康。因此含有錒系元素的核廢料的處置是一個至關重要的課題。
錒系元素是第89號元素錒到103號元素鐒共15种放射性元素的統稱。錒系元素也屬於過渡元素,只是錒系元素的外層和次外層的電子構型基本相同,新增加的電子則大都填入了從外側數第三個電子層(即5f電子層)中,所以錒系元素又可以稱為5f系。為了區別於元素週期表中的d區過渡元素,故又將錒系元素及鑭系元素合稱為內過渡元素。由於錒系元素都是金屬,所以又可以和鑭系元素統稱為f區金屬。錒系元素用符號An表示。